Various "header" routines renamed to "preamble" because it's more accurate.
Fixed dependencies on "preamble" routines
Chunked-encoding only sent for HTTP/1.1 requests to /api/transactions/*
Ignoring SIGPIPE
write() errors while sending responses are caught
Message type moved into its own file, along with helper routines, in prep to unify use of the type between response.c/request.c
URL/path/query attributes of message_t now dynamically sized
Generalized extend_string routine, message body dynamically allocated