add deps to the make all clause

this is just to stop full rebuilds all the time
add a cursor high visible command

this allows the caller to set the cursor on and blinking in one go
(useful for curses integration). Note this blinks the whole char segment
so the char under the cursor appears, then the segment is all black,
then the char appears again (unfortunately the LCD does not support
underline just blinking)
Merge pull request #1 from coherentsolutions/master

new high vis cursor cmd & twik makefile