Fixed major bug: drivers that accepted size arguments could wind

up with more than 80 characters (20x4) in their display, and thus
overwrite memory outside of the allocated 80 characterwframebuffer.

For example, using a 20x6 screen would do this.

All drivers now either ignore a missing framebuffer, or allocate it
themselves - the latter is prefered.

server/drivers/stv5730.c

@@ -447,9 +447,8 @@ stv5730_init (struct lcd_logical_driver *driver, char *args)
     memset (driver->framebuf, 0, STV5730_WID * STV5730_HGT);
 
     driver->cellwid = 4;
-    driver->cellhgt = 6;	// FIXME: stv5730->cellwid always stays 5
-    // regardless what it is set to here. This is
-    // a bug but not inside this driver.
+    driver->cellhgt = 6;
+
     driver->clear = stv5730_clear;
     driver->string = stv5730_string;
     driver->chr = stv5730_chr;