Add the ability for MCStreamer to emit comments on the same line as directives.

Switch over the asm-verbose comment for double values to use it.  We now get:

_x:
	.long	343597384                                   ## double 1.231200e+02
	.long	1079953326

For example, note that the comment is on the same line as the .long.  Woo.

llvm-svn: 94166