swift234

Don't allow overloading on @noreturn, @noescape of function parameters

Overloading on the function parameter being 'throws' is still permitted.

Note that the explicit check for overloading on the 'throws' of the
_declaration itself_ was dead code. We were already stripping out the
ExtInfo from the top level function type when building the
OverloadSignature's InterfaceType.

Fixes <rdar://problem/19816831>.

Swift SVN r28482