RFR: 8029434: Spliterator of Stream returned by BufferedReader.lines() should have NONNULL characteristic

[Henry Jen]

Hi,

Please review a small fix that add missing NONNULL characteristic and 
cleanup in javadoc.

Thanks Anthony Vanelverdinghe for reporting of this bug.

http://cr.openjdk.java.net/~henryjen/tl/8029434/0/webrev/

Cheers,
Henry