diagnostics: introduce diagnostic-macro-unwinding.h/cc

diagnostics: introduce diagnostic-macro-unwinding.h/cc

Eliminate a dependency on "tree" from the code used by
diagnostic_path handling.

No functional change intended.

gcc/ChangeLog:
	* Makefile.in (OBJS): Add diagnostic-macro-unwinding.o.

gcc/c-family/ChangeLog:
	* c-opts.cc: Replace include of "tree-diagnostic.h" with
	"diagnostic-macro-unwinding.h".

gcc/ChangeLog:
	* diagnostic-macro-unwinding.cc: New file, with material taken
	from tree-diagnostic.cc.
	* diagnostic-macro-unwinding.h: New file, with material taken
	from tree-diagnostic.h.
	* tree-diagnostic-path.cc: Repalce include of "tree-diagnostic.h"
	with "diagnostic-macro-unwinding.h".
	* tree-diagnostic.cc (struct loc_map_pair): Move to
	diagnostic-macro-unwinding.cc.
	(maybe_unwind_expanded_macro_loc): Likewise.
	(virt_loc_aware_diagnostic_finalizer): Likewise.
	* tree-diagnostic.h (virt_loc_aware_diagnostic_finalizer): Move
	decl to diagnostic-macro-unwinding.h.
	(maybe_unwind_expanded_macro_loc): Likewise.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>