Add -fdump*-folding suboption.

2017-05-25  Martin Liska  <mliska@suse.cz>

	* dumpfile.c: Add TDF_FOLDING.
	* dumpfile.h (enum dump_kind): Likewise.
	* genmatch.c (dt_simplify::gen_1): Use it.

From-SVN: r248452