mingw32-libxml2 security update

2.7.6-6 - Synchronize patch-set with mainline-version. - Bump version to 5, 6. Related: rhbz891477 2.7.6-4 - Change release number to 4. - Added patch libxml2-Fix-an-off-by-one-pointer-access.patch - Added patch libxml2-Fix-a-segfault-on-XSD-validation-on-pattern-error.patch - Added patch...