wx: Fix LDFLAGS for Mac

MacOSX min version must be applied to LDFLAGS otherwise linking with static
wxWidgets libraries doesn't work.
wx: Fix crash when garbage collect event handlers (debugger caused seg fault)

wxStyledTextCtrl had no wrapper class so, because it was not detected
that it had virtual destructors, thus references to it was not cleaned
up on destruction. When a process dies and wx cleans up the event handlers
access was made to the deleted object and caused a seg fault.

Added a testcase which I thought could provoke the bug but didn't.
wx: Remove compiler option -fomit-frame-pointer on Darwin

Causes a segfault when building on 10.9 with -mmacosx-version-min=10.9
wx: Fix hanging wx calls

wxWakeUpIdle doesn't always work on wxGTK and the workaround is to
periodically invoke it, so the gui-thread doesn't get stuck in poll.

Previously it was only called when NOT in batch mode, however if the
wxWakeUpIdle call after a batch_begin command did not wake up the
thread it would still get stuck in poll.
Prepare release