Mouse-friendly functions bar for meters panel

Before:
SpaceStyle EnterMove  DelDeleteEscDone  |
~~~~~      ~~~~~      ~~~      ~~~      |
UpUp     DnDown  LtLeft  RtRight EnterConfirmDelDeleteEscDone  |
~~       ~~      ~~      ~~      ~~~~~       ~~~      ~~~      |

After:
SpaceStyle EnterMove                                           DelDeleteF10Done
~~~~~      ~~~~~      ~~                                       ~~~      ~~~
SpaceStyle EnterLock  UpUp    DnDown  <-Left  ->Right          DelDeleteF10Done
~~~~~      ~~~~~      ~~      ~~      ~~      ~~      ~~       ~~~      ~~~

* Align 'Delete' and 'Done' to the right to match functions on other
  screens. (Accidental clicking is avoided as a side benefit.)
* You could change meter type while in moving mode. New bar now hints
  this.
* Two Enter key functions are put in the same place and so mouse clicks
  there act like functions toggle. (The wording change to 'Lock' is
  also to reflect this.)
* '<-' and '->' instead of 'Lt' and 'Rt' abbreviation as the latter is
  not widely seen and arrows shapes are obvious. :)
* 'Esc' key for 'Done' in this context may not be intuitive, comparing
  to 'F10'. While I wish there be a Cancel/Undo function for 'Esc', it
  wouldn't hurt if we write 'F10' for 'Done' on functions bar for now.

MetersPanel.c

@@ -33,13 +33,17 @@ struct MetersPanel_ {
 
 // Note: In code the meters are known to have bar/text/graph "Modes", but in UI
 // we call them "Styles".
-static const char* MetersFunctions[] = {"Style ", "Move  ", "Delete", "Done  ", NULL};
-static const char* MetersKeys[] = {"Space", "Enter", "Del", "Esc"};
-static int MetersEvents[] = {' ', 13, KEY_DC, 27};
-
-static const char* MetersMovingFunctions[] = {"Up    ", "Down  ", "Left  ", "Right ",  "Confirm", "Delete", "Done  ", NULL};
-static const char* MetersMovingKeys[] = {"Up", "Dn", "Lt", "Rt", "Enter", "Del", "Esc"};
-static int MetersMovingEvents[] = {KEY_UP, KEY_DOWN, KEY_LEFT, KEY_RIGHT, 13, KEY_DC, 27};
+static const char* MetersFunctions[] = {"Style ", "Move  ", "                                       ", "Delete", "Done  ", NULL};
+static const char* MetersKeys[] = {"Space", "Enter", "  ", "Del", "F10"};
+static int MetersEvents[] = {' ', 13, ERR, KEY_DC, KEY_F(10)};
+
+// We avoid UTF-8 arrows ← → here as they might display full-width on Chinese
+// terminals, breaking our aligning.
+// In <http://unicode.org/reports/tr11/>, arrows (U+2019..U+2199) are
+// considered "Ambiguous characters".
+static const char* MetersMovingFunctions[] = {"Style ", "Lock  ", "Up    ", "Down  ", "Left  ", "Right ", "       ", "Delete", "Done  ", NULL};
+static const char* MetersMovingKeys[] = {"Space", "Enter", "Up", "Dn", "<-", "->", "  ", "Del", "F10"};
+static int MetersMovingEvents[] = {' ', 13, KEY_UP, KEY_DOWN, KEY_LEFT, KEY_RIGHT, ERR, KEY_DC, KEY_F(10)};
 static FunctionBar* Meters_movingBar = NULL;
 
 static void MetersPanel_delete(Object* object) {

MetersPanel.h

@@ -29,6 +29,10 @@ struct MetersPanel_ {
 
 // Note: In code the meters are known to have bar/text/graph "Modes", but in UI
 // we call them "Styles".
+// We avoid UTF-8 arrows ← → here as they might display full-width on Chinese
+// terminals, breaking our aligning.
+// In <http://unicode.org/reports/tr11/>, arrows (U+2019..U+2199) are
+// considered "Ambiguous characters".
 
 void MetersPanel_setMoving(MetersPanel* this, bool moving);