plugins: Improve usability of iPod keymaps

- Reduce need to press multiple buttons at
the same time to quit a plugin

- Have "Menu" be default way to quit plugins or
to access plugin menu

- Fall back to (Long) "Select" or Long "Menu"
in cases where Menu button isn't available
(e.g. in ImageViewer and many games)

out of scope:
boomshine, lua_scripts, Rockpaint,
Doom, Duke3D, Pacbox, Quake,
Sgt-Puzzles, Wolf3D, XWorld,
Minesweeper, Pixel Painter, Spacerocks

Change-Id: I6d4dc7174695fe4b8ee9cbaccb21bdbfe6af5c48

manual/plugins/rocklife.tex

@@ -30,7 +30,8 @@ ignored.
       \opt{HAVEREMOTEKEYMAP}{& \PluginRCLeft}
     & Status (only when paused)\\
 
-    \PluginCancel
+    \nopt{IPOD_4G_PAD,IPOD_3G_PAD}{\PluginCancel}
+    \opt{IPOD_4G_PAD,IPOD_3G_PAD}{\ButtonMenu}
       \opt{HAVEREMOTEKEYMAP}{& \PluginRCCancel}
     & Exit\\
 \end{btnmap}