kvm: added ShowCursor and HideCursor, fixed off-by-one error in ClrEol
lined: color prompts, fix editing existing strings.
sq: switched to delphi syntax for generics
stri.pas: added boolstr
ll: removed unit reference in specialization to work around new fpc behavior
rings: generics cleanup.

- switched to delphi syntax
- un-nested all the GNode types (couldn't manage it for GCursor yet)
- made GRing a subclass of GNode and removed GRingNode
- added a default indexed property to GRing
- added test_rings.pas