gas macro arg1 test

A number of targets pad out the data section, and there are targets
that have 2 or 4 octets per byte.  And some even that don't have '#'
as a line comment char.  tic6x-elf fails the test with "Error: too
many positional arguments".

	* testsuite/gas/macros/arg1.s: Pad out data section.  Use C style
	comments.
	* testsuite/gas/macros/arg1.d: Adjust to suit.  Don't run on
	multi-octet per byte targes.  xfail tic6x.