Fix gen-make.py to run on Windows without SWIG.
Fix gen-make.py to run on Windows without SWIG.

* build/generator/gen_win.py
 (GeneratorWin.__init__): Update to allow building without SWIG.
 Report a warning if SWIG is not installed



git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@856046 13f79535-47bb-0310-9956-ffa450edef68

wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion