Merge r2921:2922 from SDL trunk to 1.2 branch: mingw alloca.h workaround.

--HG--
branch : SDL-1.2
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/branches/SDL-1.2%402244

configure.in

@@ -124,7 +124,14 @@ if test x$enable_libc = xyes; then
     fi
 
     dnl Checks for library functions.
+    case "$host" in
+    *-*-cygwin* | *-*-mingw32*)
+        ;;
+    *)
         AC_FUNC_ALLOCA
+        ;;
+    esac
+
     AC_FUNC_MEMCMP
     if test x$ac_cv_func_memcmp_working = xyes; then
         AC_DEFINE(HAVE_MEMCMP)