Merge branch 'en/incl-forward-decl'

Code hygiene improvement for the header files.

* en/incl-forward-decl:
  Remove forward declaration of an enum
  compat/precompose_utf8.h: use more common include guard style
  urlmatch.h: fix include guard
  Move definition of enum branch_track from cache.h to branch.h
  alloc: make allocate_alloc_state and clear_alloc_state more consistent
  Add missing includes and forward declarations

object-store.h

@@ -1,6 +1,7 @@
 #ifndef OBJECT_STORE_H
 #define OBJECT_STORE_H
 
+#include "cache.h"
 #include "oidmap.h"
 #include "list.h"
 #include "sha1-array.h"