swift234

reapply r30789, r30795, r30796, r30797, without r30787 which causes a compile time hit:

 - Produce more specific diagnostics relating to different kinds of invalid
 - add a testcase, nfc
 - Reimplement FailureDiagnosis::diagnoseGeneralMemberFailure in terms of

Not including r30787 means that we still generate bogus diagnostics like:
[1, 2, 3].doesntExist(0)  // expected-error {{type 'Int2048' does not conform to protocol 'IntegerLiteralConvertible'}}

But it is an existing and separable problem from the issues addressed here.



Swift SVN r30819