remove INT_MAX limit on the n argument to snprintf/swprintf

remove INT_MAX limit on the n argument to snprintf/swprintf

this was a POSIX requirement that was always in conflict with ISO C,
which specified a well-defined behavior for snprintf and swprintf so
long as the actual number of bytes/characters produced did not exceed
INT_MAX.

I originally raised this conflict for snprintf with the Austin Group
as tracker issue 761, which was never resolved. it was later reported
again as issue 1219, and as a result the conflicting requirement has
been removed.

the corresponding issue with swprintf does not seem to have been
addressed, but as the same reasoning applies to it, I am removing the
limitation on n for swprintf as well.