enhance llvm-mc -show-inst to print the enum of an instruction, like so:

	testb	%al, %al                ## <MCInst #2412 TEST8rr
                                        ##   <MCOperand Reg:2>
                                        ##   <MCOperand Reg:2>>
	jne	LBB1_7                  ## <MCInst #938 JNE_1
                                        ##   <MCOperand Expr:(LBB1_7)>>

llvm-svn: 95935