Blender Git Loki

Cleanup: Rename BKE_libblock_relink, and move it to BKE_library_remap.h

Was a waaaaayyyyy to much generic name for such a specific func, renamed
to much more descriptive BKE_libblock_relink_to_newid().

In near future (few weeks, to limit as much as possible silent mismatch
in branches), will rename BKE_libblock_relink_ex to BKE_libblock_relink,
this is the real generic data-block relinking func!