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/stringimpl.h

@@ -87,13 +87,6 @@ extern WXDLLIMPEXP_DATA_BASE(const wxStringCharType*) wxEmptyStringImpl;
     #undef wxUSE_STD_STRING
     #define wxUSE_STD_STRING 1
 
-    // the versions of std::string included with gcc 2.95 and VC6 (for which
-    // _MSC_VER == 1200) and eVC4 (_MSC_VER == 1201) lack clear() method
-    #if (defined(__GNUG__) && (__GNUG__ < 3)) || \
-        !wxCHECK_VISUALC_VERSION(7) || defined(__EVC4__)
-        #define wxSTRING_BASE_HASNT_CLEAR
-    #endif
-
     typedef wxStdString wxStringImpl;
 #else // if !wxUSE_STL_BASED_WXSTRING