swift234

[func-sig-opts] Add SILArgument::isSelf() and SILFunction::hasSelfArgument().

SILFunction::hasSelfArgument() returns true if the SILFunction has a
calling convention with self.

SILArgument::isSelf() returns true if the SILArgument is the last
argument of the first BB of a function for which
SILFunction::hasSelfArgument() is true.

Swift SVN r22378