swift234

Call a standard library entry point from initializer stubs.

Rather than simply trapping with no output, have the initializer stubs
call into a new standard library function _unimplemented_initializer
that emits a more reasonable diagnostic, containing the name of the
class, the name of the initializer, and the file/line/column where the
class itself is defined. This finishes <rdar://problem/16156996>.



Swift SVN r15049