Osc: Fix the cross-correlation transform.
     It was taking the channel arguments in the wrong order.
Osc: Add "Peak" markers to the Cross-Correlation transform
plugins/fmcomms2_adv: Add TX Monitor

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Osc: Fix bug that crashes app when creating new plot
     - Happends only when optimization level of the gcc is below -O2
     - Fix is: get the size of the window when we are sure that the window is realized.
     - Fix 2: inexplicably a segmentation fault occurs when extracting a gchar value from a tree model.