Do not apply scalar storage order to pointer fields

Do not apply scalar storage order to pointer fields

Pointer fields (and vector fields originally) were not really considered
when the scalar_storage_order attribute, so they are swapped as well.
As pointed out, this is problematic to describe in DWARF and probably
not very useful in any case, so this pulls them out.

gcc/
	* doc/extend.texi (scalar_storage_order): Mention effect on pointer
	and vector fields.
	* tree.h (reverse_storage_order_for_component_p): Return false if
	the type is a pointer.
gcc/c/
	* c-typeck.c (build_unary_op) <ADDR_EXPR>: Do not issue an error
	on the address of a pointer field in a record with reverse SSO.
gcc/testsuite/
	* gcc.dg/sso-12.c: New test.