Disable warnings in LLDBWrapPython.cpp with -Werror.

When -Werror is used, we don't have control over the generated
code from SWIG, and it often has warnings.  Just disable them for
this file when -Werror is used, they are usually not important
anyway.

Differential revision: https://reviews.llvm.org/D25246

llvm-svn: 283343