Merge branch 'jk/drop-release-pack-memory'

Merge branch 'jk/drop-release-pack-memory'

xmalloc() used to have a mechanism to ditch memory and address
space resources as the last resort upon seeing an allocation
failure from the underlying malloc(), which made the code complex
and thread-unsafe with dubious benefit, as major memory resource
users already do limit their uses with various other mechanisms.
It has been simplified away.

* jk/drop-release-pack-memory:
  packfile: drop release_pack_memory()