Reset multilingual environment of Emacs to the default status.
The default status is as follows:
The default value of `buffer-file-coding-system' is nil.
The default coding system for process I/O is nil.
The default value for the command `set-terminal-coding-system' is nil.
The default value for the command `set-keyboard-coding-system' is nil.
The order of priorities of coding systems are as follows:
utf-8
iso-2022-7bit
iso-latin-1
iso-2022-7bit-lock
iso-2022-8bit-ss2
emacs-mule
raw-text