conn.h: option filed in CONNECTION struct is now UINT16.

conn-func.h: add accessor Macros

Conn_OPTION_ADD( conn, CONN_OPTION )
Conn_OPTION_DEL( conn, CONN_OPTION )
Conn_OPTION_ISSET( conn, CONN_OPTION )

To add, remove or test for a certain option field attribute (e.g. CONN_ISCLOSING)
These Macros should be used instead of accessing conn->options directly.