expr.c (do_store_flag): Remove special case folding for single bit tests.

expr.c (do_store_flag): Remove special case folding for single bit tests.

	* expr.c (do_store_flag): Remove special case folding for
	single bit tests.  Instead call back into the commonized folder
	routine.
	* fold-const.c (fold_single_bit_test): New function, mostly
	extracted from do_store_flag, with an additional case extracted
	from fold.
	(fold): Call fold_single_bit_test appropriately.
	* tree.h (fold_single_bit_test): Prototype.

From-SVN: r68867