Added support to the Objective-C language runtime
to find Objective-C class types by looking in the
symbol tables for the individual object files.

I did this as follows:

- I added code to SymbolFileSymtab that vends
  Clang types for symbols matching the pattern
  "_OBJC_CLASS_$_NSMyClassName," making them
  appear as Objective-C classes.  This only occurs
  in modules that do not have debug information,
  since otherwise SymbolFileDWARF would be in
  charge of looking up types.

- I made a new SymbolVendor subclass for the
  Apple Objective-C runtime that is in charge of
  making global lookups of Objective-C types.  It
  currently just sends out type lookup requests to
  the appropriate SymbolFiles, but in the future we
  will probably extend it to query the runtime more
  completely.

I also modified a testcase whose behavior is changed
by the fact that we now actually return an Objective-C
type for __NSCFString.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@145526 91177308-0d34-0410-b5e6-96231b3b80d8
13 files changed