Visibility support for Clang was disabled in 7198c33 because of linking
errors when building shared libraries, related to non-inline methods in
exported template classes.
The last Clang version to have these problems is version "4.1
(tags/Apple/clang-421.11.66)" as part of Xcode 4.5.2, and the next
release fixes them (version "4.2 (clang-425.0.24)", Xcode 4.6). Check
for the Clang version and only disable visibility support when compiling
with Apple Clang < 4.2.
Note that Apple Clang 4.2 is based on official Clang 3.2 so also check
for that version in case of non-Apple builds. The only official Clang
that has been tested successfully is 3.4 which worked fine with
visibility. Other versions that were tried (3.1 and 3.2) segfault while
compiling wx.
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
