display: add class CDisplay

This should fix broken build with --enable-lcd (BOXMODEL_OSMIO4KPLUS)

FIXME: CLCD::setVolume() needs fix because it contains no code.

The concept to overwrite CVFD with CLCD should be thought over, see:

display.h:

#if BOXMODEL_OSMIO4KPLUS
#include <driver/lcdd.h>
#define CVFD CLCD
#else
#include <driver/simple_display.h>
#endif

A plan with base- and subclasses and overwritable members should be
more sustainable. It will be coming to a mess, and if not yet, it will
be at some point, especially since nothing was documented.

src/driver/display.h

@@ -13,3 +13,19 @@
 #ifdef ENABLE_GRAPHLCD
 #include <driver/glcd/glcd.h>
 #endif
+
+
+#ifndef __DISPLAY_H__
+#define __DISPLAY_H__
+
+class CDisplay
+{
+	public:
+		CDisplay(){};
+		virtual ~CDisplay(){};
+
+		virtual void showServicename(const std::string, const bool ){}; // UTF-8
+		virtual void showServicename(const std::string, int){}; // UTF-8
+};
+
+#endif

src/driver/lcdd.h

@@ -39,7 +39,7 @@
 #endif
 #include <driver/file.h>
 #endif // LCD_UPDATE
-
+#include "display.h"
 #include <configfile.h>
 #include <pthread.h>
 
@@ -132,7 +132,7 @@ typedef enum
 class CLCDPainter;
 class LcdFontRenderClass;
 
-class CLCD
+class CLCD : public CDisplay
 {
 	public:
 
@@ -244,6 +244,7 @@ class CLCD
 		/** blocks for duration seconds */
 		void showRCLock(int duration = 2);
 		void showVolume(const char vol, const bool perform_update = true);
+		void setVolume(const char /*vol*/){printf("#### FIXME: __function__, at __FILE__ ###\n");}; // FIXME: fake member to fix build with --enable-lcd
 		void showPercentOver(const unsigned char perc, const bool perform_update = true, const MODES m = MODE_TVRADIO);
 		void showMenuText(const int position, const char *text, const int highlight = -1, const bool utf_encoded = false);
 		void showAudioTrack(const std::string &artist, const std::string &title, const std::string &album);

src/driver/vfd.h

@@ -39,13 +39,13 @@
 #endif
 #include "driver/file.h"
 #endif // VFD_UPDATE
-
+#include "display.h"
 #include <pthread.h>
 #include <string>
 
 #include <cs_frontpanel.h>
 
-class CVFD
+class CVFD : public CDisplay
 {
 	public: