Initial import of Tim Brom's threadsafe parsers.

Titus,

I have some other commits after this, but these are the first ones I did on the branch. The first 5 can be ignored. They come from when I was testing some of the issue tracker integration stuff. (Maybe I could probably rebase them away, since the fifth one cancels the first four - i.e., I removed a test file that I created.) The sixth commit is just adding the files I grabbed from Tim's smp_filtering branch. (He also added some build support to lib/Makefile, which is in a subsequent commit. But, this set of commits should be fairly inert - shouldn't affect the functioning of your code in any way.)

Eric