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/chip8emulator.tex

@@ -43,7 +43,8 @@ The default keymappings are:
           ,GIGABEAT_PAD,MROBE100_PAD,SANSA_FUZE_PAD,SANSA_FUZEPLUS_PAD}
             {\ButtonPower}
         \opt{GIGABEAT_S_PAD}{\ButtonBack}
-        \opt{PBELL_VIBE500_PAD,SAMSUNG_YH92X_PAD,SAMSUNG_YH820_PAD}{\ButtonRec}
+        \opt{PBELL_VIBE500_PAD}{\ButtonRec}
+        \opt{SAMSUNG_YH92X_PAD,SAMSUNG_YH820_PAD}{\ButtonRew}
         \opt{MPIO_HD200_PAD}{\ButtonRec + \ButtonPlay}
         \opt{MPIO_HD300_PAD}{Long \ButtonMenu}
         \end{sideways}
@@ -51,6 +52,7 @@ The default keymappings are:
         % Key "0" 
         \begin{sideways}
         \opt{SANSA_FUZEPLUS_PAD}{\ButtonVolDown}
+        \opt{SAMSUNG_YH92X_PAD,SAMSUNG_YH820_PAD}{\ButtonFF}
         \end{sideways}
         &
         % "Key "1"