Blender Git Loki

[#13726] Segfault with (Re)Appending objects
fix this by freeing the lib-file-data after linking or appending, re-appending will be slower now
(as slow as appending for the first time).

Not strictly needed, set the memory for bhead's to zero in readfile.c since comparisons are done later on with this data making valgrind complain.

Added some missing headers too.