Update all BigInt methods using c_longs to use int.
Update all BigInt methods using c_longs to use int.

Inside the methods, use safe_cast to convert to c_long safely.

hildeth/chapel,CoryMcCartan/chapel,CoryMcCartan/chapel,hildeth/chapel,hildeth/chapel,CoryMcCartan/chapel,chizarlicious/chapel,hildeth/chapel,hildeth/chapel,hildeth/chapel,CoryMcCartan/chapel,hildeth/chapel,chizarlicious/chapel,chizarlicious/chapel,chizarlicious/chapel,chizarlicious/chapel,CoryMcCartan/chapel,CoryMcCartan/chapel,chizarlicious/chapel,CoryMcCartan/chapel,chizarlicious/chapel