Added the AsmToken::Hash enum constant to MCAsmLexer.h in preparation of

Added the AsmToken::Hash enum constant to MCAsmLexer.h in preparation of
supporting other targets.  Changed the code to pass MCAsmInfo to the parser
and the lexer.  Then changed the lexer to use CommentString from MCAsmInfo
instead of a literal '#' character.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81046 91177308-0d34-0410-b5e6-96231b3b80d8