Work around for missing __attribute((alias))

Some platforms such as OSX 10.7 don't have __attribute((alias)) enabled.
We need a work around there

configure.ac

@@ -25,13 +25,17 @@ AC_C_CONST
 AC_TYPE_SIZE_T
 
 AM_ICONV
-
 # add -DHAVE_INCONV to CFLAGS. We should not use #include <config.h> in
 # public headers
 if test "$am_cv_func_iconv" = "yes"; then
        CFLAGS="$CFLAGS -DHAVE_ICONV"
 fi
 
+AM_GCC_ATTRIBUTE_ALIAS
+if test "$am_cv_gcc_have_attribute_alias" = "yes"; then
+      CFLAGS="$CFLAGS -DHAVE_ATTRIBUTE_ALIAS"
+fi
+
 dnl no optional stuff by default
 OPTDIRS=""