Add a lock to individual cells. A lock on a cell will prevent it from
being redrawn by reporting it as clean. This will be true until the lock
has been removed. When a lock is removed, the cell is also marked as
dirty in order to force a redraw.
fixes#578
Also, while here, create a look up table
for performance reasons. This can be suppressed by a new
TCELL_MINIMIZE environment variable, if RAM is precious.
Tcell applications should work out of the box by default
for most users in East Asian locales now.
* SetContent() now makes a copy of the combining characters slice. Avoids unexpected side effects when original slice is reused/modified. Fixes#215
* Appending combining characters to an empty rune slice instead of making a copy.
fixes#38 Broke wide characters in last update
fixes#39 Clean up logic for encodings, enhance fallback options
fixes#36 Support more mouse buttons on Windows.
