Merge branch 'remove-bcc-support'

Remove support for Borland C++ compiler, it wasn't tested since a long
time and probably didn't work anyhow and there was no interest in
keeping support for it since many years.

See https://github.com/wxWidgets/wxWidgets/pull/2087

interface/wx/app.h

@@ -1181,7 +1181,7 @@ wxAppDerivedClass& wxGetApp();
     Notice that this function is only available if @c wxUSE_ON_FATAL_EXCEPTION
     is 1 and under Windows platform this requires a compiler with support for
     SEH (structured exception handling) which currently means only Microsoft
-    Visual C++ or a recent Borland C++ version.
+    Visual C++.
 
     @header{wx/app.h}
 */