access C structures via a camlp4 extension

Cstruct is a library and syntax extension to make it easier to access C-like structures directly from OCaml. It supports both reading and writing to these structures, and they are accessed via the Bigarray module.

An example pcap description is:

cstruct pcap_header {
  uint32_t magic_number;   (* magic number *)
  uint16_t version_major;  (* major version number *)
  uint16_t version_minor;  (* minor version number *)
  uint32_t thiszone;       (* GMT to local correction *)
  uint32_t sigfigs;        (* accuracy of timestamps *)
  uint32_t snaplen;        (* max length of captured packets, in octets *)
  uint32_t network         (* data link type *)
} as little_endian