<rdar://problem/13506727>

Symbol table function names should support lookups like symbols with debug info.

To fix this I:
- Gutted the way FindFunctions is used, there used to be way too much smarts only in the DWARF plug-in
- Made it more efficient by chopping the name up once and using simpler queries so that SymbolFile and Symtab plug-ins don't need to do as much
- Filter the results at a higher level
- Make the lldb_private::Symtab able to chop up C++ mangled names and make as much sense out of them as possible and also be able to search by basename, fullname, method name, and selector name.