patch to fix regression on header size with large headers introduced by support of <server-id> and <http-headers>. This should ensure we have at least space for 2kB of extra headers. Depending on function and call we may have much more space.

Please test this very carefully.
Some pointers what should be in the tests (NOT complet list):
- request to 'static' web/ and admin/ pages.
- requests to playlist generation.
- requests to streams.
- requests to admin/ manipulation functions.
- test everything with at least 8kB of extra headers, then reduce in 1kB (or 512B) steps.
- see if response is correct OR 500 is returned.
- run under valgrind or similar to see no buffer overflow or similiar will happen.
- take a cookie!

svn path=/icecast/trunk/icecast/; revision=19300