Ability to use a waflib.zip file with waf-zip entry point
Changes:
- created waf-zip entry point
- waflib.zip can created by doing::
zip waflib -9 waflib/*.py waflib/Tools/*.py waflib/extras/*.py
- the wscript also builds waflib.zip
- allow selecting which core tools to use (saves 31k for C/C++ only)
By default, everything is included.
- altered module loading functions to allow loading modules from a zip file.
