[boost] [HEAD] [patch] BoostBook update WARNING for WIN32 in Python Script

I just noticed that the WARNING for WIN32 users of BoostBook points to an old URL of the xslt-proc for win32. Attached is a trivial patch to change the warning. -- Dean Michael C. Berris http://cplusplus-soup.blogspot.com/ mikhailberis AT gmail DOT com +63 928 7291459