...when showing the refactoring marker and generating the quick fix
operations.

Opening main.cpp

  main.cpp:
   #include "file.h"
   void f(char *s) { foo(s); }

  file.h:
    // significant line 1
    // significant line 2
    // significant line 3
    bool foo(int fd);

led to

    SOFT ASSERT: "textBlock.isValid()" in file
    clangdiagnosticmanager.cpp, line 205

and a misbehavior when applying the fixit from the tooltip.

We take the line of a diagnostic to display the fixit marker if it has
any fixits. But the (child) diagnostic might be issued for an other file
(that's what happening here), so better take the line of the location
where the fixit is meant to be applied.

Same applies for generation of the quick fix entries.

Change-Id: I48d38420b285d2d2f86e3faa2319513aa8b47848
Reviewed-by: Christian Kandeler <christian.kandeler@theqtcompany.com>
Reviewed-by: David Schulz <david.schulz@theqtcompany.com>