Allow "Zoom Area" to be clicked out of axes like Scilab 5.3.0

Reported by McLavy

Originally assigned to Caio SOUZA

Since version 5.4.*, "Zoom Area" can not be set out of axes, which makes zooming very inconvenient. For example:

a = gca()
a.data_bounds = [0,0;1,2]

To zoom in where near the axes, say x=0.01 or y=0.01, the mouse has to move extremely slowly and carefully to be not out of range--the zooming cross will loose focus.

In previous versions, the first click could be at (-1,-1) though that point is not plotted. But the operation is much easier.

In other words, what we can do in previous version is:

data_bounds = [x_lo,y_lo ; x_hi,y_hi]
zooming click at (x,y)

if x<x_lo then x=x_lo
if x>x_hi then x=x_hi

if y<y_lo then y=y_lo
if y>y_hi then y=y_hi

However current version does allow that. If the click (x,y) is not within the data_bounds, then nothing will do.