Forgot to use the last argument of printf.
Added a consistent newline between the for loops.
Fixed using wrong format in printf.
Forgot to add 2 for some reason.
Removed the resolution check. It's unnecessary.
Doubled the amount of loops.
Made time_diff and other functions depending on it unsigned.
Made the functions in test.c static.
Removed unnecessary restricts and 2nd version of empty_sstring.

Restrict on a pointer that is the only argument in a function seems to do no performance speed up
Removed s_memnull.

I see almost no use of this and I don't think it needs to be in a library about strings.
Removed mem{cpy,move}.

..because they are already in string.h and it would be hard making them faster than in there and a waste of effort.
Removed functions using uint abuse.