add --vcmanifest flag (yes/no) for VC8 build support to embed manifest

* win32/configure.js win32/Makefile.msvc: add --vcmanifest flag (yes/no)
  for VC8 build support to embed manifest within files. Under MS VC, build
  libxml2_a_dll.lib by default (LIBXML_STATIC_FOR_DLL flag).

svn path=/trunk/; revision=3625