Finalized math.E and math.Pi.

Without this treatment these constants will not be inlined
or folded, bloating bytecode and inhibiting optimization.
Marking them @inline doesn't have any additional effect, but
I did it to futurize them in light of SI-7542.
Merge pull request #2618 from paulp/pr/final-in-package-object

Finalized math.E and math.Pi.