- Generic content modification scheme:

 - Generic content modification scheme:
   Each feature has its own applicability flag that is set
   from csp->action->flags.
   Replaced the "filtering" int flag , by a function pointer
   "content_filter" to the function that will do the content
   modification. If it is != NULL, the document will be buffered
   and processed through *content_filter, which must set
   csp->content_length and return a modified copy of the body
   or return NULL (on failiure).
 - Changed csp->is_text to the more generic bitmap csp->content_type
   which can currently take the valued CT_TEXT or CT_GIF
 - Reformatting etc
 - Removed all #ifdef PCRS