decl.c (gnat_to_gnu_field): Post the error message for parent overlapping on the position instead of on the...

	* gcc-interface/decl.c (gnat_to_gnu_field): Post the error message
	for parent overlapping on the position instead of on the first bit.
	For a field that needs strict alignment, issue the error for the
	position first and, for the size, issue an error if it is too large
	only for the atomic and aliased cases.  Issue a specific error if
	the size is not a multiple of a byte in the volatile and the stric
	alignment cases.

From-SVN: r219009