WMaker: rationalised the use of flags for window icons in the switchpanel
The flags were stored as 'char' but it is more logical to use int which is
"the natural size for integer on the host" and may help future evolution
if new flags are added;
The array is created with an initial size consistent with the number of
element we feed it with in 'makeWindowFlagsArray', this avoids a bunch
of realloc;
Fixed the type conversion that was not right, as pointed by clang.
Signed-off-by: Christophe CURIS <christophe.curis@free.fr>