Call 'awk' instead of 'gawk' for cross-platform compatibility.

Call `awk` instead of `gawk` for cross-platform compatibility. Linux systems normally have a symbolic link from `awk` to `gawk`, so there should be no difference in the functionality on those systems.
Merge pull request #700 from jack-pappas/patch-1

Call 'awk' instead of 'gawk' for cross-platform compatibility.