Hardcode Linux 2.5.46 base version requirement.

Linux 2.5.46 was circa 2003.

The requirement was already enforced in tracer.c:80 via commit
5ef1eca8d78eea302c2fb82a9d755973cd6bd8ce. This commit just enforces that
consistently and removes unnecessary checks.
Merge pull request #496 from batrick/parrot-kernel-version

Hardcode Linux 2.5.46 base version requirement.