OpenSystemsDevelopment / qpdf

This requires a special build option.

Having it at compile time breaks cross-compilation and isn't really
right anyway.

This was broken for cross-compilation and has probably been
unnecessary for several years now.

Also fix extraneous whitespace in related some tests.

Use autoconf rather than ifdefs to determine what format string to use
for long long.

Fixes qpdf/qpdf#417

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.

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.