Edit TestCMockC.c so it will (mostly) run on 16-bit platforms.

This is useful when testing embedded code, and trying to gain
confidence that CMock works correctly, is configured correctly,
etc.

This involved creating cmock_internal.h which holds #defines
used by cmock.c. These are then also used in TestCMockc.c
instead of hard-coded data sizes.
Merge pull request #14 from canton7/feature/test-on-other-platforms

Edit TestCMockC.c so it will (mostly) run on 16-bit platforms. (Very nice work, Antony)