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