Added support for objective C built-in types: id, Class, and SEL. This

involved watching for the objective C built-in types in DWARF and making sure
when we convert the DWARF types into clang types that we use the appropriate
ASTContext types.

Added a way to find and dump types in lldb (something equivalent to gdb's 
"ptype" command):

    image lookup --type <TYPENAME>

This only works for looking up types by name and won't work with variables.
It also currently dumps out verbose internal information. I will modify it
to dump more appropriate user level info in my next submission.

Hookup up the "FindTypes()" functions in the SymbolFile and SymbolVendor so
we can lookup types by name in one or more images.

Fixed "image lookup --address <ADDRESS>" to be able to correctly show all
symbol context information, but it will only show this extra information when
the new "--verbose" flag is used.

Updated to latest LLVM to get a few needed fixes.

llvm-svn: 110089