OpenSystemsDevelopment / qpdf

Thanks to Zdenek Dohnal <zdohnal@redhat.com> for contributing the code
used for the gnutls crypto provider.

Includes updates to m4/ax_cxx_compile_stdcxx.m4 to make it work with
msvc, which supports C++-11 with no flags but doesn't set __cplusplus
to a recent value.

Now that there aren't any more...

Based on sizeof(size_t). Assumes 64 if not 32.

If set, we avoid using Windows I/O HANDLE, which is disallowed in some
versions of the Windows SDK, such as for Windows phones.
QUtil::same_file will always return false in this case. Only applies
to Windows builds.