(set-language-info): If LANG-ENV is
the current one, don't call set-language-environment, but call one
of set-language-environment-XXX to make INFO effective now.
(set-language-environment): Call set-language-environment-XXX
functions instead of doing the various setups directly.
(set-language-environment-coding-systems): Argument eol-type
deleted.
(set-language-environment-input-method)
(set-language-environment-nonascii-translation)
(set-language-environment-charset)
(set-language-environment-fontset)
(set-language-environment-unibyte): New functions.