- added delayed open/read functionality (so that SSI code can delay sending of a file until internal data is available);
- clean up fs-handling: additional read is not required with our current fs implementation;
- kill oldest connection when running out of http_state memory;
- splitted SSI state into its own struct so that non-SSI pages don't consume too much memory (SSI buffer can get quit big);
- added support for HTTP/1.1 persistent connections (use the '-11' switch of makefsdata; not available for SSI files since we cannot calculate the file length in advance);
- splitted the unreadably-long function http_send_data into multiple smaller functions;
