texture mapping on prims.  Credits to DaveP

HttpStatus unit tests have never caused a unit test failure but
they do have the word 'error' in their text descriptions which
gets picked up by the log processor in TC builds.  So, reactivate
the tests and reform the descriptions.

I'm calling this the more correct fix.  The httprequest tests
actually talk to an HTTP server running in the Python test
scaffold script.  Under severe CPU competition, it may not
get the cycles needed to start up and make progress.  So this
modifies the test to spin a little faster and dwell waiting
on the server for a longer period.  Hope this will be
adequate to make the tests reliable.

library has new exception-throwing behavior when a client disconnects
unannounced.  Generally ignore exceptions as a result as we don't
care about the server side.  On HTTP trace-mode tests, spin a little
faster and longer to give libcurl time to emit all the junk it wants
to send us.  Should reduce 'reasonable time' failures on tests <12>
and <13>.

made marker file lock use append, not truncate