simple_sprintf() -> snprintf() and fix format specifier / datatype for time_t

[michaelortmann]

Found by: michaelortmann Patch by: michaelortmann Fixes:

One-line summary: simple_sprintf() -> snprintf() and fix format specifier / datatype for time_t

Additional description (if needed): See also: https://github.com/eggheads/eggdrop/blob/541e8ac17e549a40e177b5eea54e4abf24629a33/src/botmsg.c#L138-L141

eggdrops simple_sprintf() brings a %D specifier for converting int to base64. Those are harder to migrate to snprintf(). But all others should be migrated over time. One benefit is indeed that the compiler will be able to do more checks.

Test cases demonstrating functionality (if applicable):