Incorrect parsing of integer constants like `2e1`

[lmbarros]

Context

Originally mentioned in #4481 (comment) , moving to a separate issue.

Failure Information (for bugs)

Steps to Reproduce

This program

main :: proc() {
	i: int = 2e1
	j: int = 2.2e1
	fmt.printfln("%v, %v", i, j)
}

gives me this result:

10, 22

I'd expect 2e1 to be 20.

[dislux-hapfyl]

package test
import  "core:fmt"
main :: proc()  {
    x: int = 2.e1
    y: int = 2.2e1
    fmt.printfln("%v, %v", x, y)
}

20,22

You forgot the period.