removed debugging cruft, added README and stub headers for standalone testing

[fb-resolver] / README

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+This began as a cleanup of a few startling bugs in resolver.c, but I encountered so many other endemic issues (IMO) along the way that I just started from the top and groomed everything on my way through.  Apologies if the style doesn't quite match the rest of the codebase, but I hope it's at least a little easier to follow.
+
+The resolver is still architected the same as the original (id est, a group of threads, all feeding from a common input stream in turn, resolving their data and responding independently before repeating), but it strives to do the things it does a little more correctly.
+
+I've probably screwed up portability somewhere, and it may now require a non-vintage compiler.
+
+
+Major fixes:
+
+       * locking.  original had none around its core data structures (!)
+       * functions no longer harbor static buffers (!)
+       * non-blocking IO is more resilient
+
+
+Other changes:
+
+       * uses modern socket framework
+       * can cache successful lookups as well as failures
+       * cache lookups are now less than linear
+       * uses native stdio locking
+
+
+Possible future improvements to consider:
+
+       * track more internal data, dump stats on a signal
+       * make the threadpool dynamically sized
+       * use a different work-queue model entirely
+