Problem: Various inconsistencies in test files.
Solution: Add modelines where they were missing. Use Check commands instead
of silently skipping over tests. Adjust indents and comments.
(Ken Takata, closes#6695)
Problem: assert_fails() checks the last error message.
Solution: Check the first error, it is more relevant. Fix all the tests
that rely on the old behavior.
Problem: Crash when using garbagecollect() in between rand().
Solution: Redesign the rand() and srand() implementation. (Yasuhiro
Matsumoto, closes#5587, closes#5588)
