Define kwsys_ios_binary macro for std::ios::binary

The 'binary' openmode does not exist on all compilers.  We define macro
<kwsys>_ios_binary, where <kwsys> is the KWSys namespace, to refer to
std::ios::binary if it exists and 0 otherwise.  Sample usage:

  kwsys_ios::ifstream fin(fn, kwsys_ios::ios::in | kwsys_ios_binary);