* Underscores `_` may be placed between two digits in a int/float literal
* Consecutive underscores are not allowed
* Fixed parsing bug in exponents of hexadecimal float literals.
Exponents should always be base 10, but hex characters would be parsed
inside the exponent and everything after them would be ignored. eg:
`0x1.0p1ab1` would be parsed as `0x1.0p1`.