More work on translating message expressions.

More work on translating message expressions.

Still to do:

- Chris will fix a bug in the rewriting engine for nested stmts. For example, the following:

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

tranlates to:

    NSAutoreleasePool * pool = objc_msgSend(objc_msgSend(objc_getClass("NSAutoreleasePool"), sel_getUid("alloc")), sel_getUid("init"))utoreleasePool"), sel_getUid("alloc")) init];

...which is correct, except there is garbage after sel_getUid("init"). This is because the rewriter isn't updating the extent of the containing message expression.

- Do the crazy cast thang.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@43316 91177308-0d34-0410-b5e6-96231b3b80d8