Incorrect warning for private lfun

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=6553

Reported by @marcus

If I make a function like this:

static private string _sprintf(int mode) { ... }

then the compiler gives me a warning:

Warning: _sprintf is private but not used anywhere.

But the warning is incorrect. _sprintf is used as an lfun.