Merge branch 'jh/apply-free-patch'

Valgrind reports quite a lot of discarded memory inside apply.
Fix them, audit and document the buffer ownership rules.

By Junio C Hamano (8) and Jared Hance (1)
* jh/apply-free-patch:
  apply: document buffer ownership rules across functions
  apply: tighten constness of line buffer
  apply: drop unused macro
  apply: free unused fragments for submodule patch
  apply: free patch->result
  apply: release memory for fn_table
  apply: free patch->{def,old,new}_name fields
  apply: rename free_patch() to free_patch_list()
  apply: do not leak patches and fragments