only sets MEM_IntReal if the integer value will fit in 6 bytes or less.
Fix for ticket [ba2f4585cf495231]
FossilOrigin-Name: 2b221bb15fd2b9f6a426e5eb439f7dbabbe3c4cab010c49b87dae3bb1f16c081
the intreal() SQL function in testfixture. Write a few simple tests to
prove this all works. TH3 will hold most of the INTREAL tests, probably.
FossilOrigin-Name: c9838731325e0ca73bd8784c10c74ae043fed7861e6de269fd90e29fa4a19955