Not all Content-IDs are surrounded by <...>, such as those from Outlook
Extend MakeClicky's HTML avoidance hack to avoiding anything that looks like an attribute

For example, alt="http://example.com" should never be auto-linked.  This
was seen in the wild.

MakeClicky really needs to become fully HTML aware instead of resorting
to this hack, but for now this makes it incrementally better.
Merge branch '4.2/html-display-nits'