Changed the X86 assembler for intel syntax to work with directional labels.

The X86 assembler has a separate code to parser the intel assembly syntax
in X86AsmParser::ParseIntelOperand().  This did not parse directional labels.
And if something like 1f was used as a branch target it would get an
"Unexpected token" error.

The fix starts in X86AsmParser::ParseIntelExpression() in the case for
AsmToken::Integer, it needs to grab the IntVal from the current token
then look for a 'b' or 'f' following the Integer.  Then it basically needs to
do what is done in AsmParser::parsePrimaryExpr() for directional
labels.  It saves the MCExpr it creates in the IntelExprStateMachine
in the Sym field.

When it returns to X86AsmParser::ParseIntelOperand() it looks
for a non-zero Sym field in the IntelExprStateMachine and if
set it creates a memory operand not an immediate operand
it would normally do for the Integer.

rdar://14961158