Over the years we've skipped more and more of the tests in
llhttpclient_test.cpp (nee llhttpclient_tut.cpp) because they've relied on
particular behaviors from Internet sites not under our control.
We skipped a test that fetches llsd+xml from secondlife.com because
"secondlife.com is not reliable enough for unit tests."
We skipped a test that tries to observe a failure with "http://www.invalid"
because some local ISPs turn "no such domain" DNS errors into valid pages
offering the requester to buy the specified domain name.
Today we've had to skip tests attempting to contact "http://www.google.com"
for reasons we haven't yet diagnosed, but that probably have to do with
Google's IPv6 rollout.
Use local temp server test_llsdmessage_peer.py as the success destination,
eliminating DNS, Internet access and remote server behavior as failure modes.
Use idle localhost port for failure test.
Re-enable all skipped LLHTTPClient tests!
Re-enable on Windows!
In support of these tests, modify test_llsdmessage_peer.py:
Support HEAD as no-data variant of GET.
Change GET result dict to avoid resembling an error response -- confusing.
Make GET/POST return actual dict rather than undecorated string "success".
Because of that last, change llcapabilitylistener_test.cpp and
llsdmessage_test.cpp to extract "reply" key from response rather than
expecting response to be a string itself.

indra/test/llhttpclient_tut.cpp ==> indra/llmessage/tests/llhttpclient_test.cpp,
with corresponding CMakeLists.txt changes in their respective directories.
This first commit merely moves the test source file without changing it --
separating out moves from edits simplifies code review.

Today, 2012-06-06, LLHTTPClient::get("http://www.google.com/") has stopped
working. This is unrelated to viewer code changes: it crosses repo boundaries.
Skip the afflicted tests to get builds working until we can recast the tests
to avoid the flaky dependency.