VE: add @ command

blk/124

@@ -8,3 +8,6 @@ be sure, then press 'E'.
 'R' goes into replace mode at current cursor position.
 Following keystrokes replace current character and advance
 cursor. Press return to return to normal mode.
+
+'@' re-reads current block even if it's dirty, thus undoing     
+recent changes.

blk/128

@@ -10,3 +10,4 @@
 : $h -1 cmv ; : $l 1 cmv ; : $k -64 cmv ; : $j 64 cmv ;
 : $H EDPOS @ 0x3c0 AND pos! ;
 : $L EDPOS @ 0x3f OR pos! ;
+: $@ BLK> @ BLK@* @ EXECUTE 0 BLKDTY ! contents ;