(build-describe-language-support-function,

(build-describe-language-support-function,
build-set-language-environment-function): The functions deleted.
(set-language-info): Doc-string modified.  Chage handling of
special keys describe-function and setup-function.
(read-language-name): Return nil if a language specified does not
have KEY.
(current-input-method-title): Doc-string modified.
(select-input-method): Set current-input-method to nil even if
inactivation of the current input method failed.
(set-language-environment): Doc-string modified.
(describe-language-support): Doc-string modified.  Calls an
appropriate function for each langauge.
(describe-language-support-internal): New function.