So far we have assumed that:
 1) The main diagnostic explains the issue.
 2) The child diagnostics might have fixits attached that use the
    imperative in the text. Because of this we made the fixit texts
    clickable.

As it turns out, the main diagnostic itself also might have fixits
attached, as the following example shows.

  // Parse solely with the warning option "-Weverything"
  template <typename T> struct C {};
  C<C<int>> bla;

...which leads to

  warning: consecutive right angle brackets are incompatible with C++98
  (use '> >')

...which has no further child diagnostics, but provides a fixit.

The problem with this case is that it is not obvious for the user that
clicking the text will fix the issue since no imperative is used at
start of the text. For now, handle this case by making the text of the
main diagnostic clickable, too. But if we encounter more cases like
this, we probably should visualize the "you can apply the fix by
clicking here" concept differently.

Change-Id: Ia64e9821df783cba13d32395fab19251feca0398
Reviewed-by: Alessandro Portale <alessandro.portale@theqtcompany.com>