[llvm] r174983 - [ms-inline asm] Add support for lexing binary integers with a [bB] suffix.

[Rafael Espíndola]

> This patch also limits backward labels to [0-9]b, so that only 0b and 1b are
> ambiguous.
> Part of rdar://12470373

Unfortunately this broke firefox (see llvm.org/pr15266), so I have reverted it.

Cheers,
Rafael