Remove MSVC6 support.

Don't support this compiler any more, this allows to get rid of tons of
MSVC6-specific workarounds, in particular we can now use Bind() and natural
template functions calls in the library code.

Also remove MSVC6 project and solution files and don't generate them when
bakefile_gen is ran any more (removing the remaining occurrences of msvc6prj
from the bakefiles results in weird bake-time errors, so it's simpler to just
leave them there).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76532 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/seh.h

@@ -55,9 +55,8 @@
     extern void wxSETranslator(unsigned int code, EXCEPTION_POINTERS *ep);
 
     // up to VC 12 this warning ("calling _set_se_translator() requires /EHa")
-    // is harmless and it's easier to suppress it than use different makefiles
-    // for VC5 and 6 (which don't support /EHa at all) and VC7+ (which does
-    // accept it but it seems to change nothing for it anyhow)
+    // is harmless and it's easier to suppress it than deal with it as make/
+    // project file level as it seems to be harmless
     #if __VISUALC__ < 1900
         #pragma warning(disable: 4535)
     #endif