[PATCH] Include path enumeration

[PATCH] Include path enumeration

https://gcc.gnu.org/ml/gcc-patches/2017-10/msg00693.html
	gcc/
	* incpath.h (enum incpath_kind): Name enum, prefix values.
	(add_path, add_cpp_dir_path, get_added_cpp_dirs): Use incpath_kind.
	* incpath.c (heads, tails): Use INC_MAX.
	(add_env_var_paths, add_standard_paths): Use incpath_kind.
	(merge_include_chains, split_quote_chain,
	register_include_chains): Update incpath_kind names.
	(add_cpp_dir_path, add_path, get_added_cpp_dirs): Use incpath_kind.
	* config/darwin-c.c (add_system_framework_path): Update incpath_kind
	names.
	(add_framework_path, darwin_register_objc_includes): Likewise.
	* config/vms/vms-c.c (vms_c_register_includes): Likewise.
	gcc/c-family/
	* c-opts.c (add_prefixed_path): Change chain to incpath_kind.
	(c_common_handle_option): Update incpath_kind names.
	gcc/fortran/
	* cpp.c (gfc_cpp_add_include_path): Update incpath_e names.
	(gfc_cpp_add_include_path_after): Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@253654 138bc75d-0d04-0410-961f-82ee72b054a4