#1 Stay close to setlocale(3)

[Sir Raorn]

If empty string is passed to to setlocale as locale_val
argument, change locale according to env. vars. and
return current value(s). If nil is passed, query and
return current values withoud alterning anythig.

This patch just allows passing of bil value to
Locale::setlocale().

[Sir Raorn]

Patch for Locale::setlocale to allow pass nil as locale_val.