tree-ssa-strlen.c: Include expr.h.

tree-ssa-strlen.c: Include expr.h.

	* tree-ssa-strlen.c: Include expr.h.
	(get_stridx): Don't use c_strlen, instead use string_constant
	and compute string length from it.
	* Makefile.in (tree-ssa-strlen.o): Depend on $(EXPR_H).

From-SVN: r180574