Work around IE's broken 'hasAttribute'

Review Request #183 — Created Dec. 6, 2007 and submitted — Latest diff uploaded

Review Board SVN (deprecated)
261, 279
Internet Explorer silently fails all calls to <node>.hasAttribute, which causes Review Board's line-comment system to fail.  A decent workaround is to use getAttribute instead, as that will return either null or "" when the attribute doesn't exist (depending on the DOM implementation), which are both boolean-false.

This fix was suggested by Mark Dewing in issue 261.
I verified that comments work on the following platforms:
    RHEL5, Firefox
    WinXP, Firefox
    WinXP, Internet Explorer 6.0 SP2
    Vista, Internet Explorer 7.0