Add zstd support for LTO bytecode compression.

Add zstd support for LTO bytecode compression.

2019-07-03  Martin Liska  <mliska@suse.cz>

	* Makefile.in: Define ZSTD_LIB.
	* common.opt: Adjust compression level
	to support also zstd levels.
	* config.in: Regenerate.
	* configure: Likewise.
	* configure.ac: Add --with-zstd and --with-zstd-include options
	and detect ZSTD.
	* doc/install.texi: Mention zstd dependency.
	* gcc.c: Print supported LTO compression algorithms.
	* lto-compress.c (lto_normalized_zstd_level): Likewise.
	(lto_compression_zstd): Likewise.
	(lto_uncompression_zstd): Likewise.
	(lto_end_compression): Dispatch in between zlib and zstd.
	(lto_compression_zlib): Mark with ATTRIBUTE_UNUSED.
	(lto_uncompression_zlib): Make it static.
	* lto-compress.h (lto_end_uncompression): Fix GNU coding style.
	* lto-section-in.c (lto_get_section_data): Pass info
	about used compression.
	* lto-streamer-out.c: By default use zstd when possible.
	* timevar.def (TV_IPA_LTO_DECOMPRESS): Rename to decompression
	(TV_IPA_LTO_COMPRESS): Likewise for compression.

From-SVN: r272996