Add compatibility for Turbo C 2.0 and QuickC 2.0

This is interesting since these compilers are from right around the same
year when the ANSI C standard was adopted.

src/llmedian.c:
    * Added a couple of casts to satify QuickC.

src/phone.c:
    * Fixed the position of the overflow bit. (Off-by-one)
    * Added another cast to pacify QuickC.

src/rand.c:
    * Let's just stick to one 16-bit calculation for simplicity.

src/subarray.c:
    * Changed a couple of longs into ints since it made more since.
      Thanks, Turbo C, for pointing it out. When you're on an arch where
      int and long are practically the same size, you'd never catch such
      a thing unless you paid really, really, really close attention...