RFR: 8231122: @index tag with newline causes tag search to fail

[Hannes Wallnöfer]

Please review:

JBS: https://bugs.openjdk.java.net/browse/JDK-8231122
Webrev: http://cr.openjdk.java.net/~hannesw/8231122/webrev.00/

This causes any sequence of whitespace characters to be reduced to a single spece character in the index tag text, and to be removed from the HTML anchor name.

Thanks,
Hannes