Change the X86 backend to stop using the evil ADDC/ADDE/SUBC/SUBE nodes (which

Change the X86 backend to stop using the evil ADDC/ADDE/SUBC/SUBE nodes (which
their carry depenedencies with MVT::Flag operands) and use clean and beautiful
EFLAGS dependences instead.

We do this by changing the modelling of SBB/ADC to have EFLAGS input and outputs
(which is what requires the previous scheduler change) and change X86 ISelLowering
to custom lower ADDC and friends down to X86ISD::ADD/ADC/SUB/SBB nodes.

With the previous series of changes, this causes no changes in the testsuite, woo.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122213 91177308-0d34-0410-b5e6-96231b3b80d8