Suppress Clang analyzer warnings about dead assignments

The last assignment in the series is indeed dead, but for consistency
I want to keep it around.

src/gmenu2x.cpp

@@ -356,6 +356,7 @@ void GMenu2X::initBG() {
 			serviceX -= 19;
 		}
 	}
+	(void)serviceX;
 
 	bgmain->convertToDisplayFormat();
 }

src/linkapp.cpp

@@ -496,6 +496,7 @@ void LinkApp::showManual() {
 				x = gmenu2x.drawButton(s, "right", gmenu2x.tr["Change page"], x);
 				x = gmenu2x.drawButton(s, "cancel", "", x);
 				x = gmenu2x.drawButton(s, "start", gmenu2x.tr["Exit"], x);
+				(void)x;
 
 				ss.clear();
 				ss << page+1;

src/selector.cpp

@@ -74,6 +74,7 @@ int Selector::exec(int startSelection) {
 		x = gmenu2x.drawButton(bg, "cancel", "", x);
 	}
 	x = gmenu2x.drawButton(bg, "start", gmenu2x.tr["Exit"], x);
+	(void)x;
 
 	unsigned int top, height;
 	tie(top, height) = gmenu2x.getContentArea();

src/textdialog.cpp

@@ -75,6 +75,7 @@ void TextDialog::exec() {
 	x = gmenu2x.drawButton(bg, "down", gmenu2x.tr["Scroll"], x);
 	x = gmenu2x.drawButton(bg, "cancel", "", x);
 	x = gmenu2x.drawButton(bg, "start", gmenu2x.tr["Exit"], x);
+	(void)x;
 
 	bg.convertToDisplayFormat();
 

src/textmanualdialog.cpp

@@ -86,6 +86,7 @@ void TextManualDialog::exec() {
 	x = gmenu2x.drawButton(bg, "right", gmenu2x.tr["Change page"], x);
 	x = gmenu2x.drawButton(bg, "cancel", "", x);
 	x = gmenu2x.drawButton(bg, "start", gmenu2x.tr["Exit"], x);
+	(void)x;
 
 	bg.convertToDisplayFormat();