cx16: made fileselector example into a loadable library

docs/source/todo.rst

@@ -1,8 +1,6 @@
 TODO
 ====
 
-- make fileselector example into a loadable library?
-
 - for creating libraries, something like %jmptable( block.func1, block.func2, ... ) could be useful to create a compact jump table, and possibly generating extsub definitions as well. Problem: directives cannot span multiple lines atm.
 
 - Make neo and atari targets external via configs? They are very bare bones atm so easier to contribute to if they're configurable externally? What about the pet32 target
@@ -79,6 +77,7 @@ Libraries
 Optimizations
 -------------
 
+- can we optimize const uword in expressions that is actually small enough for ubyte?  Like  const uword x=128     if var>x ...
 - Compare output of some Oscar64 samples to what prog8 does for the equivalent code (see https://github.com/drmortalwombat/OscarTutorials/tree/main and https://github.com/drmortalwombat/oscar64/tree/main/samples)
 - Multi-value returns of normal subroutines: use cpu register A or AY for the first one and only start using virtual registers for the rest.
   Can FAC then be used for floats as well again? Those are now not supported for multi-value returns.