Extends the configure check for zstd.h to also verify the zstd version,
since gcc requires features that only exist in 1.3.0 and newer.  Without
this patch we get a build error for lto-compress.c when using an old zstd
version.

	Backported from master:
	2020-09-29  Jim Wilson  <jimw@sifive.com>

	gcc/
	PR bootstrap/97183
	* configure.ac (gcc_cv_header_zstd_h): Check ZSTD_VERISON_NUMBER.
	* configure: Regenerated.