Enable match.pd dumping with -fdump-tree-original

Enable match.pd dumping with -fdump-tree-original

I noticed that, while the C/C++ frontends invoke the GENERIC match.pd
simplifications to do early folding, the debug output from
generic-match.cc does not appear in the -fdump-tree-original output,
even with -fdump-tree-original-folding or -fdump-tree-original-all. This
patch fixes that.

For example, before the patch, for the following code:

int a[2];
void bar ();
void f()
{
    if ((unsigned long)(a + 1) == 0)
        bar ();
}

on AArch64 at -O0, -fdump-tree-original-all would give:

;; Function f (null)
;; enabled by -tree-original

{
  if (0)
    {
      bar ();
    }
}

After the patch, we get:

Applying pattern match.pd:3774, generic-match.cc:24535
Matching expression match.pd:146, generic-match.cc:23
Applying pattern match.pd:5638, generic-match.cc:13388

;; Function f (null)
;; enabled by -tree-original

{
  if (0)
    {
      bar ();
    }
}

The reason we don't get the match.pd output as it stands, is that the
original dump is treated specially in c-opts.cc: it gets its own state
which is independent from that used by other dump files in the compiler.
Like most of the compiler, the generated generic-match.cc has code of
the form:

  if (dump_file && (dump_flags & TDF_FOLDING))
    fprintf (dump_file, ...);

But, as it stands, -fdump-tree-original has its own FILE * and flags in
c-opts.cc (original_dump_{file,flags}) and never touches the global
dump_{file,flags} (managed by dumpfile.{h,cc}). This patch adjusts the
code in c-opts.cc to use the main dump infrastructure used by the rest
of the compiler, instead of treating the original dump specially.

We take the opportunity to make a small refactor: the code in
c-gimplify.cc:c_genericize can, with this change, use the global dump
infrastructure to get the original dump file and flags instead of using
the bespoke get_dump_info function implemented in c-opts.cc. With this
change, we remove the only use of get_dump_info, so this can be removed.

Note that we also fix a leak of the original dump file in
c_common_parse_file. I originally thought it might be possible to
achieve this with only one static call to dump_finish () (by simply
moving it earlier in the loop), but unfortunately the dump file is
required to be open while c_parse_final_cleanups runs, as we (e.g.)
perform some template instantiations here for C++, which need to appear
in the original dump file.

We adjust cgraph_node::get_create to avoid introducing noise in the
original dump file: without this, these "Introduced new external node"
lines start appearing in the original dump files, which breaks tests
that do a scan-tree-dump-times on the original dump looking for a
certain function name.

gcc/c-family/ChangeLog:

	* c-common.h (get_dump_info): Delete.
	* c-gimplify.cc (c_genericize): Get TDI_original dump file info
	from the global dump_manager instead of the (now obsolete)
	get_dump_info.
	* c-opts.cc (original_dump_file): Delete.
	(original_dump_flags): Delete.
	(c_common_parse_file): Switch to using global dump_manager to
	manage the original dump file; fix leak of dump file.
	(get_dump_info): Delete.

gcc/ChangeLog:

	* cgraph.cc (cgraph_node::get_create): Don't dump if the current
	symtab state is PARSING.