Warn when log-scaling axes w/ zero-crossing data.

This commit adds a warning label to each PV chart that renders
text when any plot contained by the chart has input data that
contains or crosses the origin of an axes for which log-scaling
has been requested.

Change-Id: Id1eeded79db1ce1f416cb64828859552b5c55ae2
Bring VTK forwards to catch chart API addition.

... used to determine when a plot has data that
crosses or contains an axis origin.

Change-Id: Ide4d8941b06713d8947dae0a065f078f6b0e5795
Merge topic '13899_log_axis_warning' into next

fe6ce71 Bring VTK forwards to catch chart API addition.
dc7e9fb Warn when log-scaling axes w/ zero-crossing data.