Function: strtime
Section: programming/specific
C-Name: strtime
Prototype: L
Help: strtime(t): return a string describing the time t in milliseconds,
 in the format used by the GP timer.
Doc:
  return a string describing the time t in milliseconds in the format used by
  the GP timer.
 \bprog
 ? print(strtime(12345678))
 3h, 25min, 45,678 ms
 ? {
     my(t=getabstime());
     F=factor(2^256+1);t=getabstime()-t;
     print("factor(2^256+1) took ",strtime(t));
   }
 factor(2^256+1) took 1,320 ms
 @eprog
