If libz or liblzma are detected with pkg-config, AC_CHECK_HEADERS must
not be run because the correct CPPFLAGS aren't set. It is actually not
required have separate checks for LIBXML_ZLIB_ENABLED and HAVE_ZLIB_H.
Only check for LIBXML_ZLIB_ENABLED and remove HAVE_ZLIB_H macro.
Fixes bug 764657, bug 787041.
* bakefile/Readme.txt bakefile/Bakefiles.bkgen bakefile/libxml2.bkl:
files for the Bakefile generator for Makefiles from Francesco
Montorsi
* win32/configure.js: fixes for Windows compilation with non-default
flags by Joel Reed
Daniel