Test for the dl module. This only works for SunOS and Solaris.

Test for the dl module.  This only works for SunOS and Solaris.
I've attempted to make a test that silently exits if either
module dl is not present, we're not on a Sun OS, or a standard
shared library ('/usr/lib/libresolv.so') is not found...  Otherwise,
It does a simple test of dlmodule on that library.  I *think*
this would be ok to add to testall.py but I'll wait till I hear
some feedback on the liberalness of this approach.