detect __func__ properly even if CFLAGS has -Werror in it

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@4278 d0543943-73ff-0310-b7d9-9358b9ac24b2

libs/sofia-sip/configure

@@ -20453,7 +20453,7 @@ cat >>conftest.$ac_ext <<_ACEOF
 int
 main ()
 {
-char *s = __func__;
+const char *s = __func__;
 
   ;
   return 0;
@@ -26933,7 +26933,7 @@ cat >>conftest.$ac_ext <<_ACEOF
 int
 main ()
 {
-char *s = __func__;
+const char *s = __func__;
 
   ;
   return 0;

libs/sofia-sip/m4/sac-general.m4

@@ -276,7 +276,7 @@ dnl ======================================================================
 AC_DEFUN([AC_C_VAR_FUNC],
 [AC_REQUIRE([AC_PROG_CC])
 AC_CACHE_CHECK(whether $CC recognizes __func__, ac_cv_c_var_func,
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[char *s = __func__;
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[const char *s = __func__;
 ]])],[ac_cv_c_var_func=yes],[ac_cv_c_var_func=no]))
 if test $ac_cv_c_var_func = "yes"; then
 AC_DEFINE([HAVE_FUNC], 1, [Define to 1 if the C compiler supports __func__])