Enable PTA_POPCNT for Silvermont

	* config/i386/i386.c (processor_alias_table): Enable PTA_POPCNT
	for Silvermont.

	* doc/invoke.texi: Mention POPCNT for corei7, corei7-avx,
	core-avx-i, core-avx2 and slm.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@205255 138bc75d-0d04-0410-961f-82ee72b054a4