tr -[cC]s '[:upper:]' '[:lower:]'
case (or vice versa):
chars taken from s2 can be different this time
due to lack of complex upper/lower processing,
so fill string2 again to not miss some.
1st one is relatively minor: according our own manpage, upper and lower
classes must be sorted, but currently not.
2nd one is serious:
tr '[:lower:]' '[:upper:]'
(and vice versa) currently works only if upper and lower classes
have exact the same number of elements. When it is not true, like for
many ISO8859-x locales which have bigger amount of lowercase letters,
tr may do nasty things.
See this page
http://www.opengroup.org/onlinepubs/007908799/xcu/tr.html
for detailed description of desired tr behaviour in such cases.
Add some constness to avoid some warnings.
Remove use register keyword.
Deal with missing/unneeded extern/prototypes.
Some minor type changes/casts to avoid warnings.
Reviewed by: md5
