Update hash function from classic Jenkins OAAT (dict.c) and a variant of
DJB2 (hash.c) to "GoodOAAT" taken from the SMHasher repo. This hash
function passes all SMHasher tests.
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.
