For parallel LTO builds setting -fmem-report does not work very well
because all the LTRANS phases dump it in parallel and typically interleave
it to unreadability.

Since usually the memory bottleneck is WPA add a flag to only dump
the memory report for that.

gcc/:
2012-09-08  Andi Kleen  <ak@linux.intel.com>

	* gcc/common.opt (-fmem-report-wpa): Add
	* gcc/doc/invoke.texi (-fmem-report-wpa): Document.
	* gcc/lto/lto.c (do_whole_program_analysis): Run mem_report
	when mem_report_wpa is set.

From-SVN: r191095