* expr.c (store_expr): Optimize initialization of an array
	with STRING_CST.
	* expr.h (builtin_strncpy_read_str): New prototype.
	* builtins.c (builtin_strncpy_read_str): Remove prototype.
	No longer static.

	* gcc.dg/array-init-1.c: New test.

From-SVN: r127769