Port configure script to C99.

https://fedoraproject.org/wiki/Toolchain/PortingToModernC
Rebuilding configure with new autotools would also solve the problem.

cdargs-1.35_configure_c99.patch

@@ -0,0 +1,15 @@
+diff --git a/configure b/configure
+index 8567554..f4588d4 100755
+--- a/configure
++++ b/configure
+@@ -2507,8 +2507,8 @@ main ()
+   for (i = 0; i < 256; i++)
+     if (XOR (islower (i), ISLOWER (i))
+         || toupper (i) != TOUPPER (i))
+-      exit(2);
+-  exit (0);
++      return 2;
++  return 0;
+ }
+ _ACEOF
+ rm -f conftest$ac_exeext

cdargs.spec

@@ -12,6 +12,7 @@ Source1:    %{name}-%{version}_emacs-init.el
 Patch0:     %{name}-%{version}_shebangs.patch
 Patch1:     %{name}-%{version}_format_security.patch
 Patch2:     %{name}-%{version}_fix_fsf_address.patch
+Patch3:     %{name}-%{version}_configure_c99.patch
 
 BuildRequires:    gcc-c++
 BuildRequires:    ncurses-devel