Return eol-type of CODING-SYSTEM.
An eol-type is an integer 0, 1, 2, or a vector of coding systems.
Integer values 0, 1, and 2 indicate a format of end-of-line; LF, CRLF,
and CR respectively.
A vector value indicates that a format of end-of-line should be
detected automatically. Nth element of the vector is the subsidiary
coding system whose eol-type is N.
(fn CODING-SYSTEM)