(find-buffer-file-type-coding-system): For reading a file,
check for binary file, then text file, then existing file,
then whether file name is translated.
(find-buffer-file-type-coding-system):
For writing, use buffer-file-coding-system if set, otherwise
buffer-file-type.
(find-file-not-found-set-buffer-file-coding-system):
Renamed from find-file-not-found-set-buffer-file-type.
Set buffer-file-coding-system as well as buffer-file-type.
(find-binary-process-coding-system, find-buffer-file-type-match):
New functions.
(find-buffer-file-type): Use find-buffer-file-type-match.
Add find-buffer-file-type-coding-system to file-coding-system-alist
as the default entry.
Add find-binary-process-coding-system to process-coding-system-alist
as the default entry.