Disable symbols visibility support for the Clang compiler.

Even Clang++ shipped with Xcode 4.1 still can't handle visibility
of non-inline methods in exported template classes if the default
visibility is 'hidden'.

Disable visibility support for Clang for now, we'll revisit it in the future.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68471 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

build/aclocal/visibility.m4

@@ -49,6 +49,11 @@ AC_DEFUN([WX_VISIBILITY],
          error this platform has no visibility;
          #endif
 
+         /* at the time of Xcode 4.1 / Clang 3, Clang++ still didn't have the bugs sorted out: */
+         #if defined(__clang__)
+         clang compiler is still broken w.r.t. visibility;
+         #endif
+
          extern __attribute__((__visibility__("hidden"))) int hiddenvar;
          extern __attribute__((__visibility__("default"))) int exportedvar;
          extern __attribute__((__visibility__("hidden"))) int hiddenfunc (void);