Fix tests testing TEST_ASSERT_EQUAL_MEMORY_ARRAY on 16-bit platforms

The tests which exercise TEST_ASSERT_EQUAL_MEMORY_ARRAY use int arrays,
and hard-code the size of each element as 4 bytes. This is of course
untrue on 16-bit platforms.

Replace this hard-coded value with sizeof(int).
Merge pull request #47 from canton7/feature/memory-array-test-fixes

Fix tests testing TEST_ASSERT_EQUAL_MEMORY_ARRAY on 16-bit platforms. (Thanks Antony!)