Merge main(...) and runMainAndExit(...).

Commit 917a88fad06ce108a596a8fdb4607b1a2fbb3f3e changed the
visibility of runMainAndExit from public to private. The method
is only called by main and therefore runMainAndExit is not needed
anymore.
Fix JavaDoc.
Merge pull request #709 from stefanbirkner/junitcore

JUnitCore