YH8xx,YH9xx: Keymap improvement

The main "innovation" in this patch are two "virtual buttons"
for the record switch on YH92x targets. When the switch state
changes, a single BUTTON_REC_SW_ON or .._OFF button event will
be generated. Thus keymap code can react on switching, but
not on the actual state of the switch.

Wherever sensible, the following user scheme is applied:
- use PLAY as confirm button
- use REW button or Long REW to exit
- use REC (YH820) or FFWD (YH92X) as modifier key for button combos

Change-Id: Ic8d1db9cc6869daed8dda98990dfdf7f6fd5d5a1

manual/plugins/pacbox.tex

@@ -97,7 +97,8 @@ found at \url{http://www.mame.net}.
     \opt{SANSA_E200_PAD,SANSA_FUZEPLUS_PAD}{\ButtonPower}
     \opt{SANSA_FUZE_PAD}{\ButtonHome}
     \opt{GIGABEAT_PAD,GIGABEAT_S_PAD,COWON_D2_PAD,PBELL_VIBE500_PAD}{\ButtonMenu}
-    \opt{SAMSUNG_YH92X_PAD,SAMSUNG_YH820_PAD}{\ButtonRec}
+    \opt{SAMSUNG_YH92X_PAD}{\ButtonRec{} switch}
+    \opt{SAMSUNG_YH820_PAD}{\ButtonRec}
       \opt{HAVEREMOTEKEYMAP}{& }
     & Menu\\
 \end{btnmap}