stub out parser for asm files.  Change invariant on lexer to always
print its error message when it returns an asmtok::Error token.
Compute a proper error code for llvm-mc in 'lex' mode.  Add new
-as-lex option to enable lexing mode (vs parsing mode).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73859 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed