Made the expression handle variables with
DW_AT_const_value instead of a location.  Also
added a testcase covering "frame variable," "expr"
using the IR interpreter, and "expr" using the
LLVM JIT.

<rdar://problem/12978195>


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@172848 91177308-0d34-0410-b5e6-96231b3b80d8