qapitrace: fix an inline string FIXME request

Issue:
TraceLoader::callContains() had the comment
    FIXME: do string comparison directly on trace::Call
The existing code was doing a new/delete of an ApiTraceCall object
in order to use its interface for a string search.

Resolution:
Assuming what was meant by a direct comparison is using C's
strstr/strcasestr functions, that is what's implemented in
this patch.

An alternative would be to use a QString object's API
    return (QString(call->name()).contains(str, sensitivity));
but no testing was done with that.

Testing:
This code is only hit when searching in unloaded frames. Frame 0 is
pre-loaded so this code isn't exercised until the string is searched
in another frame.

Testing was done with case-sensitive and case-insensitive searches.
Compared against existing previous code for same results.

Timing:
Did two searches each of old and new code using "gettimeofday" timing
in TraceLoader::search with the following results searching for a
nonsense string (to search entire trace), case-insensitive:

warzone2100 180MB (180664407)     old         new
                                  ------      -------
Total time in seconds:            89.047      16.3269
                                  88.9844     16.3358

Signed-off-by: Lawrence L Love <lawrencex.l.love@intel.com>