`sprintf()` -> `snprintf()`

[hadley]

CRAN is starting crack down on use of sprintf() instead of snprintf() so this would be useful for us.

[evanmiller]

Is it just these three or are there other kinds of forbidden invocations?

https://github.com/search?q=repo%3AWizardMac%2FReadStat%20sprintf&type=code

[hadley]

Yeah, those were all I saw. Thanks!