Change what generates log-scale axis warnings.

Now the warning is only shown if
1. any plot has data crossing one or more axis origins,
2. log-scaling is requested on one or more of these axes, and
3. log-scaling is *not* active for those axes.

Change-Id: Id5b23caa7fbac4c1b9962b7fb40aca86905ecf15
Merge topic '13899_log_axis_warning' into next

2ba9371 Change what generates log-scale axis warnings.