doc: make i18n man and html
Allow overwrite LANGUAGE and LC_ALL make variables, for make i18n man and html.
After this patch, we can make i18n man and html by following command:
$ make clean all LANGUAGE=ja
$ hg init
$ touch unknown
$ touch a
$ hg add a
$ hg ci -m "1"
$ touch b
$ hg add b
$ hg ci -m "2"
Should show unknown
$ hg status
? unknown
$ hg revert -r 0 --all
removing b
Should show unknown and b removed
$ hg status
R b
? unknown
Should show a and unknown
$ ls
a
unknown