Fix location maybe_diag_overlap passes to diagnostics so that diagnostic pragmas...

Fix location maybe_diag_overlap passes to diagnostics so that diagnostic pragmas work better.

	PR tree-optimization/91890
	* gimple-ssa-warn-restrict.c (maybe_diag_overlap): Remove LOC argument.
	Use gimple_or_expr_nonartificial_location.
	(check_bounds_overlap): Drop LOC argument to maybe_diag_access_bounds.
	Use gimple_or_expr_nonartificial_location.
	* gimple.c (gimple_or_expr_nonartificial_location): New function.
	* gimple.h (gimple_or_expr_nonartificial_location): Declare it.
	* tree-ssa-strlen.c (maybe_warn_overflow): Use
	gimple_or_expr_nonartificial_location.
	(maybe_diag_stxncpy_trunc, handle_builtin_stxncpy_strncat): Likewise.
	(maybe_warn_pointless_strcmp): Likewise.

	* gcc.dg/pragma-diag-8.c: New test.