Properly handle number sub-types in type matching

[mraak]

number
finite - everything apart from infinity or NaN
int
bint - bigint

For example, int can be assigned to number, but not vice versa.

[getify]

Example:

var a = int`3`;
a = 4;   // error, can't assign number to int

var b = 5;
b = int`6`;   // no error

var c = finite`7`;
b = c;   // no error
c = b;   // error can't assign `number` to `finite`

[mraak]

Sent in the PR for this, have a look.