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

interface/wx/persist.h

@@ -332,9 +332,6 @@ wxPersistentObject *wxCreatePersistentObject(T *obj);
     wxPersistenceManager::Get() internally. As an additional convenience, this
     function can also set the window name.
 
-    For the implementation reasons, this function @em must be used instead of
-    the template method when using Microsoft Visual C++ 6 compiler.
-
     @param obj wxWindow-derived object to register with persistence manager and
         to try to restore the settings for.
     @param name If not empty, @a obj name is changed to the provided value