configure: check for perf_event.h version

configure: check for perf_event.h version

Intel(R) Processor Trace support requires a recent linux/perf_event.h header.

When GDB is built on an older system, Intel(R) Processor Trace will not be
available and there is no indication in the configure and build log as to
what went wrong.

Check for a compatible linux/perf_event.h at configure-time.

gdb/
	* configure.ac: Check for PERF_ATTR_SIZE_VER5 in linux/perf_event.h
	* configure: Regenerate.