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

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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94166 91177308-0d34-0410-b5e6-96231b3b80d8