[libcpp] Reimplement mkdeps data structures

https://gcc.gnu.org/ml/gcc-patches/2019-05/msg00293.html
	* include/mkdeps.h (deps_write): Add PHONY arg.
	(deps_phony_targets): Delete.
	* init.c (cpp_finish): Just call deps_write.
	* mkdeps.c (struct mkdeps): Add local vector class.  Reimplement
	vector handling.
	(munge): Munge to static buffer.
	(apply_vpath): Adjust vector handling.
	(deps_init, deps_free): Use new, delete.
	(deps_add_target): Do not munge here.  Record quoting low water mark.
	(deps_add_dep): Do not munge here.
	(deps_add_vpath): Adjust vector handling.
	(make_write_name): New.  Munge on demand here.
	(make_write_vec): New.
	(deps_phony_targets): Delete.
	(make_write): New.
	(deps_write): Forward to deps_Write.
	(deps_save, deps_restore): Adjust vector handling.

From-SVN: r270943

libcpp/include/mkdeps.h

@@ -57,7 +57,7 @@ extern void deps_add_dep (struct mkdeps *, const char *);
 
 /* Write out a deps buffer to a specified file.  The third argument
    is the number of columns to word-wrap at (0 means don't wrap).  */
-extern void deps_write (const struct mkdeps *, FILE *, unsigned int);
+extern void deps_write (const struct mkdeps *, FILE *, bool, unsigned int);
 
 /* Write out a deps buffer to a file, in a form that can be read back
    with deps_restore.  Returns nonzero on error, in which case the
@@ -70,10 +70,4 @@ extern int deps_save (struct mkdeps *, FILE *);
    in which case that filename is skipped.  */
 extern int deps_restore (struct mkdeps *, FILE *, const char *);
 
-/* For each dependency *except the first*, emit a dummy rule for that
-   file, causing it to depend on nothing.  This is used to work around
-   the intermediate-file deletion misfeature in Make, in some
-   automatic dependency schemes.  */
-extern void deps_phony_targets (const struct mkdeps *, FILE *);
-
 #endif /* ! LIBCPP_MKDEPS_H */