Don't ignore malloc failures in xmlRaiseError and xmlCopyError.
Don't print filename if context has no input.
Introduce xmlVRaiseError taking a va_list.
Private functions were previously declared
- in header files in the root directory
- in public headers guarded with IN_LIBXML
- in libxml.h
- redundantly in source files that used them.
Consolidate all private header files in include/private.