Some of the test suites use fprintf with format specifiers
that are not supported on Win32 and are not fixed by gnulib.

The mingw32 compiler also has trouble detecting ssize_t
correctly, complaining that 'ssize_t' does not match
'signed size_t' (which it expects for %zd). Force the
cast to size_t to avoid this problem

* tests/testutils.c, tests/testutils.h: Fix printf
  annotation on virTestResult. Use virVasprintf
  instead of vfprintf
* tests/virhashtest.c: Use VIR_WARN instead of fprintf(stderr).
  Cast to size_t to avoid mingw32 compiler bug
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>