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).