- Cleaned up, renamed and reorderd functions

- Cleaned up, renamed and reorderd functions
  and improved comments

- block_url:
  - Ported to CGI platform. Now delivers
    http_response or NULL
  - Unified HTML and GIF generation (moved image detection
    and GIF generation here from jcc.c:chat())
  - Fixed HTTP status to:
   -  403 (Forbidden) for the "blocked" HTML message
   -  200 (OK) for GIF answers
   -  302 (Redirect) for redirect to GIF

- trust_url:
  - Ported to CGI platform. Now delivers
    http_response or NULL
  - Separated detection of untrusted URL into
    (bool)is_untrusted_url
  - Added enforcement of untrusted requests

- Moved redirect_url() from cgi.c to here
  and ported it to the CGI platform

- Removed logentry from cancelled commit