With the move of CVM's forth to the grid protocol, we've lost the
cursor's visual indication. Now, we have it back.
The challenge now is in implementing it in SMS' text mode. In mode
4, it's easy to mark a cell as inverted, but in text mode, that's
not possible.
In VE on the SMS, the first contents line would always be cleared
because of NEWLN being called when the FBUF would spit its last
char. Inconvenient...
I've added a "graphical" mode to the grid subsystem to inhibit this
behavior in a graphical situation such as in VE.
Also, write a more complete Grid documentation.
