trace-graph: Add status bar and marker line info

Using shift and drag, a marker is made, where Marker A is green
and Marker B is red. The time stamps of the markers as well as
the delta between them is shown in a new status bar above the
graph.

Requested-by: Darren Hart <dvhltc@us.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2 files changed