Add ELT, SEARCH, MISMATCH and APROPOS, DOCUMENTATION.

And some other stuff mixed in.

If someone wants to merge the one ELT branch instead of https://github.com/Ferada/jscl/commit/4d757501022f957f4408c344c4cb895ffd073de6, feel free to, or I can change that commit around to include improvements.

SEARCH exists, but is as slow as can be. Taking the same approach as SBCL with macro magic might work, but my intention was to get APROPOS working, not optimizing SEARCH.