Changed viewport.cxx to use long instead of int like all other zoom
functions and in this succession removed the zoomtools int functions
which where only added for this one exception.

Along the way, convert the table parameter passing to using references since we are never passing
a null pointer.

Signed-off-by: Petr Mladek <pmladek@suse.cz>

Signed-off-by: Petr Mladek <pmladek@suse.cz>

Signed-off-by: Petr Mladek <pmladek@suse.cz>