make BasicScreen::{Enter,Space}Pressed() pure virtual

src/clock.h

@@ -42,6 +42,9 @@ class Clock : public Screen<Window>
 		virtual void Update();
 		virtual void Scroll() { }
 		
+		virtual void EnterPressed() { }
+		virtual void SpacePressed() { }
+		
 		virtual bool allowsSelection() { return false; }
 		
 		virtual List *GetList() { return 0; }

src/help.h

@@ -33,6 +33,9 @@ class Help : public Screen<Scrollpad>
 		
 		virtual std::string Title();
 		
+		virtual void EnterPressed() { }
+		virtual void SpacePressed() { }
+		
 		virtual bool allowsSelection() { return false; }
 		
 		virtual List *GetList() { return 0; }

src/info.h

@@ -36,6 +36,9 @@ class Info : public Screen<Scrollpad>
 		
 		virtual void Update();
 		
+		virtual void EnterPressed() { }
+		virtual void SpacePressed() { }
+		
 		virtual bool allowsSelection() { return false; }
 		
 		virtual List *GetList() { return 0; }

src/lyrics.h

@@ -52,6 +52,7 @@ class Lyrics : public Screen<Scrollpad>
 		
 		virtual void Update();
 		
+		virtual void EnterPressed() { }
 		virtual void SpacePressed();
 		
 		virtual bool allowsSelection() { return false; }

src/screen.h

@@ -47,8 +47,8 @@ class BasicScreen
 		virtual void ReadKey(int &) = 0;
 		virtual void Scroll(Where, const int * = 0) = 0;
 		
-		virtual void EnterPressed() { }
-		virtual void SpacePressed() { }
+		virtual void EnterPressed() = 0;
+		virtual void SpacePressed() = 0;
 		
 		virtual MPD::Song *CurrentSong() { return 0; }
 		

src/tag_editor.h

@@ -43,6 +43,7 @@ class TinyTagEditor : public Screen< Menu<Buffer> >
 		virtual std::string Title();
 		
 		virtual void EnterPressed();
+		virtual void SpacePressed() { }
 		
 		virtual bool allowsSelection() { return false; }