Introduce the notion of Language-based formatter prefix/suffix
This is meant for languages that share certain data types but present them in syntatically different ways, such that LLDB can now have language-based awareness of which of the syntax variations it has to present to the user when formatting those values
This is goodness for new languages and interoperability, but is NFC for existing languages. As such, existing tests cover this
llvm-svn: 249587
