When reusing an existing constant, make sure not only the value but also
the size is the same. We then also need to make a name based on the size
and value so that we can store the same value for different sizes.

Fixes problem with the bayer functions that used 255 as a 16 and 8 bit
constant. This was not detected in the unit test because both the backup
and asm functions do the same error, but it could be seen when a new
backup function was checked against a older ORC.