Expand result with type char* to string in -data-evaluate-expression

Summary:
Expand result with type char* to string in -data-evaluate-expression.
was:
  ```
    -data-evaluate-expression str
    ^done,value="0x00007fffffffece0"
  ```
now:
  ```
    -data-evaluate-expression str
    ^done,value="0x00007fffffffece0 \"hello\""
  ```

All tests pass on Linux.

Test Plan: ./dotest.py -v --executable $BUILDDIR/bin/lldb tools/lldb-mi

Reviewers: abidh

Reviewed By: abidh

Subscribers: lldb-commits, dawn, abidh

Differential Revision: http://reviews.llvm.org/D10728

llvm-svn: 240631