[libsanitizer] Added data() and capacity() getters to InternalVector.
Same interface as in STL. Needed for LSan.

Patch by Sergey Matveev (earthdok@google.com)


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@178463 91177308-0d34-0410-b5e6-96231b3b80d8