Port configure script to C99

Related to:

  <https://fedoraproject.org/wiki/Changes/PortingToModernC>
  <https://fedoraproject.org/wiki/Toolchain/PortingToModernC>

elinks-configure-c99.patch

@@ -0,0 +1,24 @@
+PR submitted upstream: https://github.com/rkd77/elinks/pull/212
+
+Author: Arjun Shankar <arjun@redhat.com>
+Date:   Fri Mar 24 14:10:43 2023 +0100
+
+    configure: Fix an "implicit int" warning
+    
+    configure defines a main function without a return type, leading to a
+    -Wimplicit-int warning (enabled by default in C99 and later dialects).
+    This commit fixes that.
+
+diff --git a/configure.ac b/configure.ac
+index d3bf724aa997173e..ef23337b34e2617f 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -390,7 +390,7 @@ void foo(const char *format, ...) {
+ 
+        exit(0);
+ }
+-main() { foo("hello\n"); }
++int main() { foo("hello\n"); }
+ ]])],[el_cv_HAVE_C99_VSNPRINTF=yes],[el_cv_HAVE_C99_VSNPRINTF=no],[el_cv_HAVE_C99_VSNPRINTF=cross])])
+ if test x"$el_cv_HAVE_C99_VSNPRINTF" = x"yes"; then
+ 	EL_DEFINE(HAVE_C99_VSNPRINTF, [C99 compliant vsnprintf()])

elinks.spec

@@ -1,7 +1,7 @@
 Name:      elinks
 Summary:   A text-mode Web browser
 Version:   0.16.0
-Release:   3%{?dist}
+Release:   4%{?dist}
 License:   GPLv2
 URL:       https://github.com/rkd77/elinks
 Source:    https://github.com/rkd77/elinks/releases/download/v%{version}/elinks-%{version}.tar.xz
@@ -49,6 +49,7 @@ Patch6: 0006-elinks-0.16.0-libidn2.patch
 
 # let list_is_singleton() return false for an empty list (#1075415)
 Patch15: elinks-0.12pre6-list_is_singleton.patch
+Patch16: elinks-configure-c99.patch
 
 %description
 Elinks is a text-based Web browser. Elinks does not display any images,
@@ -129,6 +130,9 @@ exit 0
 %{_mandir}/man5/*
 
 %changelog
+* Fri Mar 24 2023 Arjun Shankar <arjun@redhat.com> - 0.16.0-4
+- Port configure script to C99
+
 * Mon Feb 20 2023 Jan Rybar <jrybar@redhat.com> - 0.16.0-3
 - parallel builds cause FTBFS
 - Resolves: bz#2171476