Allow subclasses of specific instantiations of ObjC generic classes.

[jckarter]

If a subclass grounds all the type parameters from its base class, we don't have to worry about any erasure edge cases. We should be able to support this, giving existing code that subclasses the nongeneric form of the class a migration path. Spot-fix some places in IRGen where we assume we can't emit static references to ObjC generic classes or metaclasses.

[jckarter]

@swift-ci Please test and merge

[jckarter]

@harlanhaskins Is this failure fixed in master?

/Users/buildnode/jenkins/workspace/swift-PR-osx/swift/test/1_stdlib/UIKit.swift:48:20: error: missing argument label 'o:' in call
    printInterface(.unknown))
                   ^
                   o: 
/Users/buildnode/jenkins/workspace/swift-PR-osx/swift/test/1_stdlib/UIKit.swift:51:20: error: missing argument label 'o:' in call
    printInterface(.portrait))
                   ^
                   o: 
/Users/buildnode/jenkins/workspace/swift-PR-osx/swift/test/1_stdlib/UIKit.swift:54:20: error: missing argument label 'o:' in call
    printInterface(.portraitUpsideDown))
                   ^
                   o: 
/Users/buildnode/jenkins/workspace/swift-PR-osx/swift/test/1_stdlib/UIKit.swift:57:20: error: missing argument label 'o:' in call
    printInterface(.landscapeLeft))
                   ^
                   o: 
/Users/buildnode/jenkins/workspace/swift-PR-osx/swift/test/1_stdlib/UIKit.swift:60:20: error: missing argument label 'o:' in call
    printInterface(.landscapeRight))
                   ^
                   o: 

--

********************
Testing: 0 .. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90.. 

2 warning(s) in tests.
Testing Time: 1420.81s
********************
Failing Tests (1):
    Swift :: 1_stdlib/UIKit.swift

  Expected Passes    : 7729
  Expected Failures  : 13
  Unsupported Tests  : 344
  Unexpected Failures: 1

[harlanhaskins]

@jckarter Interesting; no it isn't, but the tests passed when we ran #2047. It's a quick fix, though.

[jckarter]

Cool, thanks @harlanhaskins.

[harlanhaskins]

The fix is #2088, by the way