Add GRUB_TIMEOUT_STYLE_BUTTON support

Suggested by Vladimir Serbinenko.

docs/grub.texi

@@ -1317,6 +1317,7 @@ case, it will show a one-line indication of the remaining time.
 
 @item GRUB_DEFAULT_BUTTON
 @itemx GRUB_TIMEOUT_BUTTON
+@itemx GRUB_TIMEOUT_STYLE_BUTTON
 @itemx GRUB_BUTTON_CMOS_ADDRESS
 Variants of the corresponding variables without the @samp{_BUTTON} suffix,
 used to support vendor-specific power buttons.  @xref{Vendor power-on keys}.
@@ -2517,15 +2518,17 @@ menu requires several fancy features of your terminal.
 @node Vendor power-on keys
 @chapter Using GRUB with vendor power-on keys
 
-Some laptop vendors provide an additional power-on button which boots another
+Some laptop vendors provide an additional power-on button which boots
-OS.  GRUB supports such buttons with the @samp{GRUB_TIMEOUT_BUTTON},
+another OS.  GRUB supports such buttons with the @samp{GRUB_TIMEOUT_BUTTON},
-@samp{GRUB_DEFAULT_BUTTON}, @samp{GRUB_HIDDEN_TIMEOUT_BUTTON} and
+@samp{GRUB_TIMEOUT_STYLE_BUTTON}, @samp{GRUB_DEFAULT_BUTTON},
-@samp{GRUB_BUTTON_CMOS_ADDRESS} variables in default/grub (@pxref{Simple
+@samp{GRUB_HIDDEN_TIMEOUT_BUTTON} and @samp{GRUB_BUTTON_CMOS_ADDRESS}
-configuration}).  @samp{GRUB_TIMEOUT_BUTTON}, @samp{GRUB_DEFAULT_BUTTON} and
+variables in default/grub (@pxref{Simple configuration}).
-@samp{GRUB_HIDDEN_TIMEOUT_BUTTON} are used instead of the corresponding
+@samp{GRUB_TIMEOUT_BUTTON}, @samp{GRUB_TIMEOUT_STYLE_BUTTON},
-variables without the @samp{_BUTTON} suffix when powered on using the special
+@samp{GRUB_DEFAULT_BUTTON}, and @samp{GRUB_HIDDEN_TIMEOUT_BUTTON} are used
-button.  @samp{GRUB_BUTTON_CMOS_ADDRESS} is vendor-specific and partially
+instead of the corresponding variables without the @samp{_BUTTON} suffix
-model-specific.  Values known to the GRUB team are:
+when powered on using the special button.  @samp{GRUB_BUTTON_CMOS_ADDRESS}
+is vendor-specific and partially model-specific.  Values known to the GRUB
+team are:
 
 @table @key
 @item Dell XPS M1330M

util/grub-mkconfig.in

@@ -190,6 +190,7 @@ export GRUB_DEFAULT \
   GRUB_DEFAULT_BUTTON \
   GRUB_HIDDEN_TIMEOUT_BUTTON \
   GRUB_TIMEOUT_BUTTON \
+  GRUB_TIMEOUT_STYLE_BUTTON \
   GRUB_BUTTON_CMOS_ADDRESS \
   GRUB_BUTTON_CMOS_CLEAN \
   GRUB_DISTRIBUTOR \

util/grub.d/00_header.in

@@ -282,17 +282,17 @@ fi
 
 make_timeout ()
 {
-    if [ "x${GRUB_TIMEOUT_STYLE}" != "x" ] ; then
+    if [ "x${3}" != "x" ] ; then
 	cat << EOF
 if [ x\$feature_timeout_style = xy ] ; then
-  set timeout_style=${GRUB_TIMEOUT_STYLE}
+  set timeout_style=${3}
   set timeout=${2}
 EOF
-	if [ "x${GRUB_TIMEOUT_STYLE}" != "xmenu" ] ; then
+	if [ "x${3}" != "xmenu" ] ; then
 	    # Fallback hidden-timeout code in case the timeout_style feature
 	    # is unavailable.  Note that we now ignore GRUB_HIDDEN_TIMEOUT
 	    # and take the hidden-timeout from GRUB_TIMEOUT instead.
-	    if [ "x${GRUB_TIMEOUT_STYLE}" = "xhidden" ] ; then
+	    if [ "x${3}" = "xhidden" ] ; then
 		verbose=
 	    else
 		verbose=" --verbose"
@@ -335,12 +335,12 @@ if [ "x$GRUB_BUTTON_CMOS_ADDRESS" != "x" ]; then
     cat <<EOF
 if cmostest $GRUB_BUTTON_CMOS_ADDRESS ; then
 EOF
-make_timeout "${GRUB_HIDDEN_TIMEOUT_BUTTON}" "${GRUB_TIMEOUT_BUTTON}"
+make_timeout "${GRUB_HIDDEN_TIMEOUT_BUTTON}" "${GRUB_TIMEOUT_BUTTON}" "${GRUB_TIMEOUT_STYLE_BUTTON}"
 echo else
-make_timeout "${GRUB_HIDDEN_TIMEOUT}" "${GRUB_TIMEOUT}"
+make_timeout "${GRUB_HIDDEN_TIMEOUT}" "${GRUB_TIMEOUT}" "${GRUB_TIMEOUT_STYLE}"
 echo fi
 else
-make_timeout "${GRUB_HIDDEN_TIMEOUT}" "${GRUB_TIMEOUT}"
+make_timeout "${GRUB_HIDDEN_TIMEOUT}" "${GRUB_TIMEOUT}" "${GRUB_TIMEOUT_STYLE}"
 fi
 
 if [ "x$GRUB_BUTTON_CMOS_ADDRESS" != "x" ] && [ "x$GRUB_BUTTON_CMOS_CLEAN" = "xyes" ]; then