For source code files with .[cChH] extension, please skip warnings meant for C++ code, so that programmers don't accidentally introduce C++-isms into their C code.

Example: readability/casting and runtime/int should be disabled for C code.

As a workaround, I am disabling these rules regardless of the source language, so that I can run cpplint more reliably across my C, C++, and mixed C/C++ projects.