fix the asmparser so that the target is responsible for skipping to

the end of the line on a parser error, allowing skipping to happen
for syntactic errors but not for semantic errors.  Before we would
miss emitting a diagnostic about the second line, because we skipped
it due to the semantic error on the first line:

  foo %eax
  bar %al

This fixes rdar://8414033 - llvm-mc ignores lines after an invalid instruction mnemonic errors

llvm-svn: 113688