We've chosen to drop our default dependence on xmlrpc. Thus we disable
the corresponding CTest submission method and remove the sources for
building xmlrpc locally. Users can re-enable the method by setting the
CTEST_USE_XMLRPC option to use a system-installed xmlrpc library.
This version of curl was added experimentally but does not address the
problem we were hoping it fixed (an occasional upload hang). Importing
a new curl can wait until the problem is fully diagnosed and addressed.