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

docs/msw/install.txt

@@ -96,11 +96,11 @@ Microsoft Visual C++ Compilation
 
 * From the IDE using the provided project files:
 
-Ready to use project files are provided for VC++ versions 6, 7, 8, 9,
-10, 11 and 12 (also known as MSVS 6, 2003, 2005, 2008, 2010, 2012 and 2013
+Ready to use project files are provided for VC++ versions 7, 8, 9,
+10, 11 and 12 (also known as MSVS 2003, 2005, 2008, 2010, 2012 and 2013
 respectively).
 
-Simply open wx_vcN.sln (for N=7, 8, 9, 10, 11 or 12) or wx.dsw (for VC6) file,
+Simply open wx_vcN.sln (for N=7, 8, 9, 10, 11 or 12) file,
 select the appropriate configuration (Debug or Release, static or DLL)
 and build the solution. Notice that when building a DLL configuration,
 you may need to perform the build several times because the projects
@@ -495,7 +495,7 @@ following to use wxWidgets:
   - _UNICODE unless you want to use deprecated ANSI build of wxWidgets.
   - NDEBUG if you want to build in release mode, i.e. disable asserts.
   - WXUSINGDLL if you are using DLL build of wxWidgets.
-* If using MSVC 6 or 7 only (i.e. not for later versions), also define
+* If using MSVC 7 only (i.e. not for later versions), also define
   wxUSE_RC_MANIFEST=1 and WX_CPU_X86.
 * Add $WXWIN/lib/prefix_lib-or-dll to the libraries path. The prefix depends
   on the compiler, by default it is "vc" for MSVC, "gcc" for g++ and so on.