SIL: Uncurry function types within the Swift type system.

Remove uncurry level as a property of SILType/SILFunctionTypeInfo. During SIL type lowering, map a (Type, UncurryLevel) pair to a Swift CanType with the uncurried arguments as a Swift tuple. For example, T -> (U, V) -> W at uncurry level 1 becomes ((U, V), T) -> W--in reverse order to match the low-level calling convention. Update SILGen and IRGen all over the place for this representation change.

SILFunctionTypeInfo is still used in the SILType representation, but it's no longer load-bearing. Everything remaining in it can be derived from a Swift type.

This is an ABI break. Be sure to rebuild clean!

Swift SVN r5296

include/swift/SIL/SILFunction.h

@@ -73,11 +73,6 @@ public:
     return LoweredType.getFunctionTypeInfo();
   }
   
-  /// Returns the uncurry level of this entry point.
-  unsigned getUncurryLevel() const {
-    return getFunctionTypeInfo()->getUncurryLevel();
-  }
-  
   /// Returns the calling convention used by this entry point.
   AbstractCC getAbstractCC() const {
     return getLoweredType().getFunctionCC();