Fix gcc warning about unsigned/signed int comparison.
Fix gcc warning about unsigned/signed int comparison.

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