swift234

Change the names of the object-literal initializers to be
semantically unambiguous.

We didn't actually intend to change how programmers normally
constructed these types, but the change to the object literal
syntax accidentally caused these initializers to have very
natural-seeming signatures.  These initializers also created
possible ambiguities with the actual initializers.  Renaming
them to refer to their function as literal initializers is the
right thing to do.

Unfortunately, this provided to be somewhat annoying, as the
code was written to assume that the argument tuple following
e.g. #colorLiteral could be directly passed to the initializer.
We solve this by hacking on both ends of the constraint system:
during generation we form a conversion constraint to the
original, idealized parameter type, and during application we
rewrite the argument tuple type to use the actual labels.
This nicely limits the additional complexity to just the
parts dealing with object literals.

Note that we can't just implicitly rewrite the tuple expression
because that would break invariants tying the labels to physical
source ranges.  We also don't want to just change the literal
syntax again and break compatibility with existing uses.

rdar://26148507