[PATCH] Move Post RA Scheduling flag bit into SchedMachineModel

[Sanjay Patel]

Hal - let me make sure we're on the same page. The last patch here is only a partial implementation of moving enablePostRAScheduler(). 

I will need to add methods to all targets that use enablePostRAScheduler() to override the defaults for:
getCriticalPathRCs()
getAntiDepBreakMode()
getOptLevelToEnablePostRAScheduler() -- this one isn't in the patch yet even in the TargetSubtargetInfo superclass, but it's necessary

I can't do this in separate commits without breaking the existing behavior of targets that override enablePostRAScheduler(). All of the those targets will need to implement their custom versions of the 3 virtual methods to maintain the current settings.

http://reviews.llvm.org/D4217