* support 3 types of end of line: Unix, Dos and old style Mac
* detect eol type automatically in detect_charset
* set buffer eol_type together with charset
* transparently convert eol sequence to \n upon reading buffers
characters in eb_nextc().
* transparently convert \n to eol sequence in eb_encode_uchar()
* handle eol types in convert-file-buffer-coding-system: either preserve
current value or force it via charset suffix -unix, -doc and -mac
* change read_charset() to accept eol_type suffix
* add eol_type and eol_char to CharsetDecodeState
* change charset methods to take CharsetDecodeState instead of charset pointers
* display eol_type in mode line if not unix