Access ProgramList more efficiently.

[Marc Alban <marcalban@…>]

A patch to access the ProgramList class more efficiently in various screens. These changes are along the same lines as the patch for #6550.

while(!list.empty()) is more efficient that while(list.count())

and

using an iterator to step through the list is O(n), while stepping through using an index (at() or [ ]) is O(n*n)

[Marc Alban <marcalban@…>]

patch to make accessing ProgramList more efficient.

[cpinkham]

(In [21392]) Access ProgramList more efficiently in various places.

Closes #6554 using patch by Marc Alban with minor tweaks by myself to get it to apply to tv_play.cpp.