Patch: TODO highlighting in comments

[Ciprian Ciubotariu]

Perhaps a dedicated user-problems toolbox might be better suitable for this 
task. (Which, by the way, I had on my own todo-list to add to KDevelop :))

Taking inspiration from other IDEs, they do support a filter on "problems" (or 
tasks in Netbeans) based on different criteria: source of the problem (the 
internal parser, user-defined comment patterns etc.), scope of the report 
(current file, current project, whole workspace/session). Add any other ideas 
you may think of for filtering :)

As a side note, I'd love to see also doxygen todos and bugs, i.e. @todo or 
@bug.