Revert "SI-6422: add missing Fractional and Integral alias in scala package"

This reverts commit c6866a28faf67cd2e455f9a0a829859a73e38819 because it adds two
members to the API and so breaks forward binary compatibility.

Attention: this is only intended for 2.10.x, not for 2.11.

Thanks to Paul Phillips for the report:
https://groups.google.com/d/topic/scala-internals/WQ0LKC8Re6A/discussion