Merge branch 'nd/no-extern'

Noiseword "extern" has been removed from function decls in the
header files.

* nd/no-extern:
  submodule.h: drop extern from function declaration
  revision.h: drop extern from function declaration
  repository.h: drop extern from function declaration
  rerere.h: drop extern from function declaration
  line-range.h: drop extern from function declaration
  diff.h: remove extern from function declaration
  diffcore.h: drop extern from function declaration
  convert.h: drop 'extern' from function declaration
  cache-tree.h: drop extern from function declaration
  blame.h: drop extern on func declaration
  attr.h: drop extern from function declaration
  apply.h: drop extern on func declaration