Various fixes for the configure script for C99 compatibility.
Most of the changes are generic in nature, due to the old version
of autoconf used by upstream (2.12).

diff --git a/configure b/configure
index db2672686719f7e1..c82ff072e4e1de5d 100755
--- a/configure
+++ b/configure
@@ -1008,7 +1008,7 @@ cross_compiling=$ac_cv_prog_cc_cross
 cat > conftest.$ac_ext <<EOF
 #line 1010 "configure"
 #include "confdefs.h"
-main(){return(0);}
+int main(){return(0);}
 EOF
 if { (eval echo configure:1014: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest; then
   ac_cv_prog_cc_works=yes
@@ -1489,8 +1489,8 @@ else
 #define TOUPPER(c) (ISLOWER(c) ? 'A' + ((c) - 'a') : (c))
 #define XOR(e, f) (((e) && !(f)) || (!(e) && (f)))
 int main () { int i; for (i = 0; i < 256; i++)
-if (XOR (islower (i), ISLOWER (i)) || toupper (i) != TOUPPER (i)) exit(2);
-exit (0); }
+if (XOR (islower (i), ISLOWER (i)) || toupper (i) != TOUPPER (i)) return 2;
+return 0; }
 
 EOF
 if { (eval echo configure:1497: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest && (./conftest; exit) 2>/dev/null
@@ -1645,7 +1645,7 @@ for ac_kw in inline __inline__ __inline; do
 #include "confdefs.h"
 
 int main() {
-} $ac_kw foo() {
+} $ac_kw int foo() {
 ; return 0; }
 EOF
 if { (eval echo configure:1652: \"$ac_compile\") 1>&5; (eval $ac_compile) 2>&5; }; then
@@ -1917,8 +1917,8 @@ else
 #define TOUPPER(c) (ISLOWER(c) ? 'A' + ((c) - 'a') : (c))
 #define XOR(e, f) (((e) && !(f)) || (!(e) && (f)))
 int main () { int i; for (i = 0; i < 256; i++)
-if (XOR (islower (i), ISLOWER (i)) || toupper (i) != TOUPPER (i)) exit(2);
-exit (0); }
+if (XOR (islower (i), ISLOWER (i)) || toupper (i) != TOUPPER (i)) return 2;
+return 0; }
 
 EOF
 if { (eval echo configure:1925: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest && (./conftest; exit) 2>/dev/null
@@ -2488,14 +2488,14 @@ else
 #include "confdefs.h"
 #include <stdio.h>
 /* If setvbuf has the reversed format, exit 0. */
-main () {
+int main () {
   /* This call has the arguments reversed.
      A reversed system may check and see that the address of main
      is not _IOLBF, _IONBF, or _IOFBF, and return nonzero.  */
   if (setvbuf(stdout, _IOLBF, (char *) main, BUFSIZ) != 0)
-    exit(1);
+    return 1;
   putc('\r', stdout);
-  exit(0);			/* Non-reversed systems segv here.  */
+  return 0;			/* Non-reversed systems segv here.  */
 }
 EOF
 if { (eval echo configure:2502: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest && (./conftest; exit) 2>/dev/null
@@ -2694,12 +2694,15 @@ else
 #include <sys/types.h>
 #include <fcntl.h>
 #include <sys/mman.h>
+#include <sys/stat.h>
+#include <stdlib.h>
+
+#ifdef HAVE_UNISTD_H
+# include <unistd.h>
+#endif
 
 /* This mess was copied from the GNU getpagesize.h.  */
 #ifndef HAVE_GETPAGESIZE
-# ifdef HAVE_UNISTD_H
-#  include <unistd.h>
-# endif
 
 /* Assume that all systems that can run configure have sys/param.h.  */
 # ifndef HAVE_SYS_PARAM_H
@@ -3032,9 +3035,9 @@ find_stack_direction ()
   else
     return (&dummy > addr) ? 1 : -1;
 }
-main ()
+int main (void)
 {
-  exit (find_stack_direction() < 0);
+  return find_stack_direction() < 0;
 }
 EOF
 if { (eval echo configure:3041: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest && (./conftest; exit) 2>/dev/null
@@ -3470,7 +3473,7 @@ else
 #include <sys/types.h>
 #include <sys/timeb.h>
 #include <stdio.h>
-main ()
+int main (void)
 {
   struct timeb s, slast;
   int c = 0;
@@ -3482,14 +3485,14 @@ main ()
       || (s.time == slast.time && s.millitm < slast.millitm)) {
       fprintf(stderr,"s: %ld, %ld, slast: %ld, %ld\n",
       	s.time,s.millitm, slast.time,slast.millitm);
-    exit (1);
+    return 1;
 	}
       if (s.time != slast.time)
     ++c;
       slast.time = s.time;
       slast.millitm = s.millitm;
     }
-  exit (0);
+  return 0;
 }
 
 EOF
diff --git a/configure.in b/configure.in
index 429677e87e99a303..0fbe252a717afb59 100644
--- a/configure.in
+++ b/configure.in
@@ -180,7 +180,7 @@ AC_CACHE_VAL(lrzsz_cv_sys_ftime_ok,
 #include <sys/types.h>
 #include <sys/timeb.h>
 #include <stdio.h>
-main ()
+int main (void)
 {
   struct timeb s, slast;
   int c = 0;
@@ -192,14 +192,14 @@ main ()
       || (s.time == slast.time && s.millitm < slast.millitm)) {
       fprintf(stderr,"s: %ld, %ld, slast: %ld, %ld\n",
       	s.time,s.millitm, slast.time,slast.millitm);
-    exit (1);
+    return 1;
 	}
       if (s.time != slast.time)
     ++c;
       slast.time = s.time;
       slast.millitm = s.millitm;
     }
-  exit (0);
+  return 0;
 }
 ],
 lrzsz_cv_sys_ftime_ok=yes,