This fixes a bug where if INCLUDE_MINIMIZED was set and the window size
was (0, 0), the window would still be excluded from the resulting list
that was created.
When getting the class/title/exe of a particular window handle in the
build_window_strings function, always set the class/title/exe pointers
to null to prevent any potential references to invalid values if any of
them do not happen to be set for whatever reason.
Because other capture methods may end up needing to share this code,
separate the window finding source code to window-helpers.c and
window-helpers.h.
This include a function to fill out a property list with windows, a
function to find a window based upon priority/title/class/exe, and a
function to decode the window title/class/exe strings from a window
setting string.
jp9000