Update the old style MSVC project files for wxWidgets itself (but not the
samples etc) from upmake instead of bakefile too, as the latest upmake version
can handle them.
Remove the Perl modules composing upmake from wxWidgets repository, it's too
difficult to maintain them both here and at https://github.com/vadz/upmake and
just keep the wxWidgets-specific upmake_script.pl here and generate
build/upmake_script itself from it using fatpack.
This also updates upmake to the latest 0.3 version, as a side effect.
