Fix a bug in llcorehttp where as put requests were getting set to POST due to setting POSTFIELDS which implies HTTP POST to curl

Fixes CMake warnings on Linux

clang correctly notes that such tests add nothing to the runtime behavior of a
program. Unfortunately, clang notes that in the form of a compile error.

Under pipelining, requests were given a 5x timeout factor due to the
way that the timeout clock works in libcurl.  Under CDN load,
connections were not being torn down quickly and it was only
this timer that led to disconnect and retry.  So, we want to
break a connection that isn't making progress but that isn't
immediately possible.  We'll compromise with a 60S timeout that
(we hope) will be neither too long for stalled connections nor
too short for large asset transfer requests.

Update to build on Xcode 6.0: clang detecting unsigned int (size_t) comparison with <0 [-Wtautological-compare]

Update to build on Xcode 6.0: interesting - clang doesn't like it if you specify extra components of a format string that aren't populated in snprintf

Incorporate the new libcurl 7.38.0 build with curl bug 1420
workaround.  Add developer-centric testing code to evaluate
the workaround or a future fix for 1420.

on the HTTP requests for inventory.  We'll benchmark with that
and see how it goes.  Document some of the history of the
background fetcher for future devs.  Suggest some future
projects to make things faster.  Pointers on using LLSD with
the llcorehttp library in the readme.  And restructured
the LLSD onCompleted() processing phases using do{}while(false)
which produced a code flow that is fairly attractive.

of used handles and a fast handle factory that's thread-
correct.

reproduce data corruption via timeouts.

as transfers can appear delayed with deep pipelining and more
requests in the pool.  Added bad HTTP status error (typically
getting a 0 back as HTTP status from libcurl) to the list of
retryable errors.  There's a response stream problem with libcurl
and pipelining that induces this problem.  Retrying helps but
may not be entirely safe.  Watch bug 1420 on the libcurl sourceforge
bug tracker.  Extend options of test/example program to include
un-ranged requests.  Document the excessive data transfer induced
when ranged requests are disabled.  This is an abnormal mode for
very rare users so we'll just eat that for now.

some problems disabling pipelining on a multi handle with outstanding
requests so build a more conservative system that allows requests
to drain before setting curl multi options.  Would rather not have
this but it is significantly safer.  "HttpPipelining" debug setting
is now fully dynamic.  Connection limits can also be made dynamic
in the near future.  Upped the default connection count back to 8 for
now but will revisit this in the tuning phase.  It might be time to
combine mesh and textures into a single asset class.  For normal
server operations that would be a clear path, but for server under
load, the current scheme may be better.  Minor cleanup in logging
to elminate some redundant strings.  Might add some more tracing to the
stall logic 'just in case'.

GetTexture and GetMesh2 at a pipeline depth of 5.  Create
global debug option, HttpPipelining, to enable and disable
HTTP pipelining (defaults to true).  Tweak texture and
mesh low- and high-water request levels based on pipelining
status and depth.  Fixup texture console which was damaged
in a recent release.  Split logging of the no-request
HTTP error case into two cases:  one for missing URL in
HTTP request, one for HTTP request not created.  A refactor
in llcorehttp is coming:  I will be moving all libcurl-
using code into libcurl-specific modules.

the change made for MAINT-2347.  Large transfers are still
10 minutes.  Add/update to-do list and add some more info to
the FAQ in the Readme.

Start using DNS cache in legacy LLCurl code.  Go to 15 seconds
particularly as we're using threaded resolver at this point.
Documentation cleanup.  Add libcurl status checking and logging
for curl_easy_setopt() operations that fail.  Shouldn't happen
and we'll just continue anyway but there's info in the logs to
track these down now.  Cleaned up logic around FASTTIMER enable
defines used to evaluate pipeline stalls in main thread.
Removed long-standing thread race around caps strings and
URL construction.  Not a significant risk but refactoring the
code to get rid of them removed one huge eyesore.  It can be
made even slicker if desired (see notes).

Last bit for this release.  Describe stream adapters and how
to select a policy class.  Slight changes to setup code to
make reality reflect documentation.

First edit complete.  Use the library in 15 minutes.  Describe the
code.  Refinements to the initial try.  Describe that code.  Still
to do:  more refinements, how to choose a policy class, FAQ.

Added toTerseString() conversion on HttpStatus to generate a string
that's more descriptive than the hex value of the HttpStatus value
but still forms a short, searchable token (e.g. "Http_503" or
"Core_7").  Using this throughout the viewer now, no live cases
of toHex(), I believe.