Add an `llvm::OStream` workalike class for use with `Logger::cout()`, with the crucial difference being special handling of `llvm::Type`s so they get printed by name rather than printing their full representation (which can be positively *huge*). This allows re-enabling some logger calls that were disabled due to extreme verbosity.

[Environment] 
DFLAGS=-I@RUNTIME_DIR@ -I@RUNTIME_DIR@/lib/common -L-L%@P%/../lib -d-version=Tango -defaultlib=@RUNTIME_AIO@ -debuglib=@RUNTIME_AIO@