Number literals can now take an optional "representation" suffix
- Use `:n` for normal numbers (IEEE-754 doubles)
- Use `:s` for signed 64 bit integers
- Use `:u` for unsigned 64 bit integers
- Other suffix will fallthrough the usual parseing logic. This means
that they will only possibly resolve to symbols if they start with -,
+, or .
The syntax does not collide with any existing valid Janet and is only
enabled with JANET_INTTYPES. This also leaves open a syntax for other
number types such as bignums, ratios, decimals, etc.
