Detect and throw Integer_overflow with OCaml

[nikochiko]

Notes from talking to KC:

• OCaml has 31 and 63-bit signed integers - one bit (LSB) is always 1 to mark it as an integer (otherwise, it is considered to be a pointer by the GC)
• OCaml also has int32 and int64 - boxed ints that are not cleared by the GC
• We should want to do it without making an expensive external C call

Ideally, the compiler should spit out code to check the overflow flag (or whatever the condition would be - with calculations on the 31/63-bit ints), and throw an exception in that case.
It would get pipelined and not cause a performance hit.