Set the default language to use when evaluating to that of the frame's CU.

* Use the frame's context (instead of just the target's) when evaluating,
  so that the language of the frame's CU can be used to select the
  compiler and/or compiler options to use when parsing the expression.
  This allows for modules built with mixed languages to be parsed in
  the context of their frame. 
* Add all C and C++ language variants when determining the language options
  to set.
* Enable C++ language options when language is C or ObjC as a workaround since
  the expression parser uses features of C++ to capture values.
* Enable ObjC language options when language is C++ as a workaround for ObjC
  requirements.
* Disable C++11 language options when language is C++03.
* Add test TestMixedLanguages.py to check that the language being used
  for evaluation is that of the frame.
* Fix test TestExprOptions.py to check for C++11 instead of C++ since C++ has
  to be enabled for C, and remove redundant expr --language test for ObjC.
* Fix TestPersistentPtrUpdate.py to not require C++11 in C.

Reviewed by: clayborg, spyffe, jingham
Subscribers: lldb-commits
Differential Revision: http://reviews.llvm.org/D11102

llvm-svn: 246829