Move macro-spellchecking code from "gcc" to new files in c-family

Move macro-spellchecking code from "gcc" to new files in c-family

The code for spellchecking macros really belongs in c-family, rather
than in gcc/spellcheck-tree.c, so this patch moves it there.

gcc/ChangeLog:
	* Makefile.in (C_COMMON_OBJS): Add c-family/c-spellcheck.o.
	* spellcheck-tree.c (find_closest_macro_cpp_cb): Move to
	c-family/c-spellcheck.cc.
	(best_macro_match::best_macro_match): Likewise.
	* spellcheck-tree.h
	(struct edit_distance_traits<cpp_hashnode *>): Move to
	c-family/c-spellcheck.h.
	(class best_macro_match): Likewise.

gcc/c-family/ChangeLog:
	* c-spellcheck.cc: New file, taken from macro-handling code in
	spellcheck-tree.c.
	* c-spellcheck.h: New file, taken from macro-handling code in
	spellcheck-tree.h.

gcc/c/ChangeLog:
	* c-decl.c: Include "c-family/c-spellcheck.h".

gcc/cp/ChangeLog:
	* name-lookup.c: Include "c-family/c-spellcheck.h".

From-SVN: r255452