swift234

[unittests] Include header for llvm::outs()

`unittests/Basic/BlotMapVectorTest.cpp` references `llvm::outs()`, which is defined in `llvm/Support/raw_ostream.h`. I believe this currently works without the import because it is transitively included via some CMake incantations and conditionals in the googletest headers invovling `GTEST_NO_LLVM_RAW_OSTREAM`. I'm not sure.

In any case, including the header is more explicit. The file uses `llvm::outs()`, so it should include the header that defines it.