Add missing prototypes to test functions.  Future compilers will not
support implicit function declarations by default, causing spurious
test failures.

The patch has been submitted to the gcrypt-devel list, but has yet to
appear in the list archives.

diff --git a/configure.ac b/configure.ac
index 6ea38f53b8548ee8..2baf25bc7d9481e6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1211,7 +1211,8 @@ AC_CACHE_CHECK([whether GCC assembler is compatible for ARM assembly implementat
                 /* Test if '.type' and '.size' are supported.  */
                 ".size asmfunc,.-asmfunc;\n\t"
                 ".type asmfunc,%function;\n\t"
-              );]], [ asmfunc(); ] )],
+              );
+	      void asmfunc(void);]], [ asmfunc(); ] )],
             [gcry_cv_gcc_arm_platform_as_ok=yes])
         fi])
 if test "$gcry_cv_gcc_arm_platform_as_ok" = "yes" ; then
@@ -1238,7 +1239,8 @@ AC_CACHE_CHECK([whether GCC assembler is compatible for ARMv8/Aarch64 assembly i
                 "eor x0, x0, x30, ror #12;\n\t"
                 "add x0, x0, x30, asr #12;\n\t"
                 "eor v0.16b, v0.16b, v31.16b;\n\t"
-              );]], [ asmfunc(); ] )],
+              );
+	      void asmfunc(void);]], [ asmfunc(); ] )],
             [gcry_cv_gcc_aarch64_platform_as_ok=yes])
         fi])
 if test "$gcry_cv_gcc_aarch64_platform_as_ok" = "yes" ; then
@@ -1267,7 +1269,8 @@ AC_CACHE_CHECK([whether GCC assembler supports for CFI directives],
                 ".cfi_restore_state\n\t"
                 ".long 0\n\t"
                 ".cfi_endproc\n\t"
-            );]])],
+            );
+	    void asmfunc(void)]])],
           [gcry_cv_gcc_asm_cfi_directives=yes])])
 if test "$gcry_cv_gcc_asm_cfi_directives" = "yes" ; then
    AC_DEFINE(HAVE_GCC_ASM_CFI_DIRECTIVES,1,
@@ -1666,7 +1669,8 @@ if test $amd64_as_feature_detection = yes; then
        [gcry_cv_gcc_as_const_division_ok],
        [gcry_cv_gcc_as_const_division_ok=no
         AC_LINK_IFELSE([AC_LANG_PROGRAM(
-          [[__asm__(".text\n\tfn:\n\t xorl \$(123456789/12345678), %ebp;\n\t");]],
+          [[__asm__(".text\n\tfn:\n\t xorl \$(123456789/12345678), %ebp;\n\t");
+	    void fn(void);]],
             [fn();])],
           [gcry_cv_gcc_as_const_division_ok=yes])])
   if test "$gcry_cv_gcc_as_const_division_ok" = "no" ; then
@@ -1679,7 +1683,8 @@ if test $amd64_as_feature_detection = yes; then
          [gcry_cv_gcc_as_const_division_with_wadivide_ok],
          [gcry_cv_gcc_as_const_division_with_wadivide_ok=no
           AC_LINK_IFELSE([AC_LANG_PROGRAM(
-            [[__asm__(".text\n\tfn:\n\t xorl \$(123456789/12345678), %ebp;\n\t");]],
+            [[__asm__(".text\n\tfn:\n\t xorl \$(123456789/12345678), %ebp;\n\t");
+	      void fn(void);]],
               [fn();])],
             [gcry_cv_gcc_as_const_division_with_wadivide_ok=yes])])
     if test "$gcry_cv_gcc_as_const_division_with_wadivide_ok" = "no" ; then
@@ -1715,7 +1720,8 @@ if test $amd64_as_feature_detection = yes; then
 		 * and "-Wa,--divide" workaround failed, this causes assembly
 		 * to be disable on this machine. */
 		"xorl \$(123456789/12345678), %ebp;\n\t"
-            );]], [ asmfunc(); ])],
+            );
+	    void asmfunc(void);]], [ asmfunc(); ])],
           [gcry_cv_gcc_amd64_platform_as_ok=yes])
         fi])
   if test "$gcry_cv_gcc_amd64_platform_as_ok" = "yes" ; then
@@ -1734,7 +1740,8 @@ if test $amd64_as_feature_detection = yes; then
               ".globl asmfunc\n\t"
               "asmfunc:\n\t"
               "xorq \$(1234), %rbp;\n\t"
-          );]], [ asmfunc(); ])],
+          );
+	  void asmfunc(void);]], [ asmfunc(); ])],
         [gcry_cv_gcc_win64_platform_as_ok=yes])])
     if test "$gcry_cv_gcc_win64_platform_as_ok" = "yes" ; then
       AC_DEFINE(HAVE_COMPATIBLE_GCC_WIN64_PLATFORM_AS,1,
@@ -1767,7 +1774,8 @@ AC_CACHE_CHECK([whether GCC assembler is compatible for Intel syntax assembly im
                 "sub eax, [esp + 4];\n\t"
                 "add dword ptr [esp + eax], 0b10101;\n\t"
                 ".att_syntax prefix\n\t"
-            );]], [ actest(); ])],
+            );
+	    void actest(void);]], [ actest(); ])],
           [gcry_cv_gcc_platform_as_ok_for_intel_syntax=yes])
         fi])
 if test "$gcry_cv_gcc_platform_as_ok_for_intel_syntax" = "yes" ; then
@@ -1832,6 +1840,7 @@ AC_CACHE_CHECK([whether GCC inline assembler supports NEON instructions],
                 "vadd.u64 %q0, %q1;\n\t"
                 "vadd.s64 %d3, %d2, %d3;\n\t"
                 );
+	    void testfn(void);
             ]], [ testfn(); ])],
           [gcry_cv_gcc_inline_asm_neon=yes])
         fi])
@@ -1879,6 +1888,7 @@ AC_CACHE_CHECK([whether GCC inline assembler supports AArch32 Crypto Extension i
 
                 "vmull.p64 q0, d0, d0;\n\t"
                 );
+	    void testfn(void);
             ]], [ testfn(); ])],
           [gcry_cv_gcc_inline_asm_aarch32_crypto=yes])
         fi])
@@ -1907,6 +1917,7 @@ AC_CACHE_CHECK([whether GCC inline assembler supports AArch64 NEON instructions]
                 "dup v0.8b, w0;\n\t"
                 "ld4 {v0.8b,v1.8b,v2.8b,v3.8b},[x0],\#32;\n\t"
                 );
+	    void testfn(void);
             ]], [ testfn(); ])],
           [gcry_cv_gcc_inline_asm_aarch64_neon=yes])
         fi])
@@ -1955,6 +1966,7 @@ AC_CACHE_CHECK([whether GCC inline assembler supports AArch64 Crypto Extension i
                 "pmull v0.1q, v0.1d, v31.1d;\n\t"
                 "pmull2 v0.1q, v0.2d, v31.2d;\n\t"
                 );
+	    void testfn(void);
             ]], [ testfn(); ])],
           [gcry_cv_gcc_inline_asm_aarch64_crypto=yes])
         fi])
@@ -2050,6 +2062,7 @@ AC_CACHE_CHECK([whether GCC inline assembler supports PowerPC AltiVec/VSX/crypto
 		    "vshasigmad %v0, %v1, 0, 15;\n"
 		    "vpmsumd %v11, %v11, %v11;\n"
 		  );
+	    void testfn(void);
             ]], [ testfn(); ] )],
           [gcry_cv_gcc_inline_asm_ppc_altivec=yes])
         fi])
@@ -2075,6 +2088,7 @@ AC_CACHE_CHECK([whether GCC inline assembler supports PowerISA 3.00 instructions
 		    "testfn:\n"
 		    "stxvb16x %r1,%v12,%v30;\n"
 		  );
+	    void testfn(void);
             ]], [ testfn(); ])],
           [gcry_cv_gcc_inline_asm_ppc_arch_3_00=yes])
         fi])