expr.c (expand_expr_real): Use usmul_optab for widening signed * unsigned multiplies.

	* expr.c (expand_expr_real): Use usmul_optab for widening
	signed * unsigned multiplies.
	* genopinit.c (optabs): Add usmul_widen_optab.
	* optabs.c (init_optabs): Likewise.
	* optabs.h (enum optab_index): Add OTI_usmul_widen.
	(usmul_widen_optab): Define.
	* config/bfin/bfin.md (usmulhisi3): New pattern.

	* doc/md.texi (usmulqihi3, usmulhisi3, usmulsidi3): Document.

From-SVN: r107258