Don't invoke reload(sys) and use StringIO objects instead of real files to capture stdin and stdout when needed (ensures all sys attributes remain unmodified after test_xmlrpc runs)

Enhancement to the new environment checking code to print the changed items under -vv. Also includes a small tweak to allow underscores in the names of resources.

an obscure, undocumentated feature so no test was added. Closes
issue #1101399.

There should be no other effect than a small decrease in memory use.
Patch by Christopher Tur Lesniewski-Laas.