Removed some commented out code from the DWARF parser.

Also reduce the size of the lldb_private::Symbol objects by removing the
lldb_private::Function pointer that was in each symbol. Running Instruments
has shown that when debugging large applications with DWARF in .o files that
lldb_private::Symbol objects are one of the highest users of memory. No one
was using the Symbol::GetFunction() call anyway.

llvm-svn: 140881