Revision 494933

LUCENE-140:

  - Add 2 more checks on initializing SegmentReader that raise
    IllegalStateException if corruption is detected.  This would have
    caught the second cause in LUCENE-140 (incorrectly re-using old
    .del files) earlier.

  - Fixed bugs in two unit tests that tripped up on these new checks.

  - Fixed (tightened) one more boundary case (when lastDoc was 0) in
    the pre-existing "docs out of order" check in SegmentMerger.java.

  - Simplified the unit test I added to TestIndexReader to test this
    issue.