Added selective logging

I wanted a way to toggle the printfs that were commented out, so I threw this together. Thoughts?

**Unlogged messages are not compiled** - _this was my main goal_
Different logging targets can be added, if desired (not sure this bit is flexible enough)
Can directly add statements if necessary (so variables can be defined for specific logging levels, see line #50 of webserver.c)

Unintentionally let a couple of changes to the RESPONSE define slip through (oops!):
* Changed Content-Type to text/html
* Added line for kicks: "Server: Haywire/master"