Move variable blink from ultralcd.h to dogm_lcd_implementation.h

to avoid warnings about unused blink.

Concentrate definitions of variables in dogm_lcd_implementation.h to one place.

Make only local used variable currentfont static.

Marlin/dogm_lcd_implementation.h

 // Maximum here is 0x1f because 0x20 is ' ' (space) and the normal charsets begin.
 // Better stay below 0x10 because DISPLAY_CHARSET_HD44780_WESTERN begins here.
 
-int lcd_contrast;
-
 // LCD selection
 #ifdef U8GLIB_ST7920
 //U8GLIB_ST7920_128X64_RRD u8g(0,0,0);
 
 #include "utf_mapper.h"
 
-char currentfont = 0;
+int lcd_contrast;
+static unsigned char blink = 0; // Variable for visualization of fan rotation in GLCD
+static char currentfont = 0;
 
 static void lcd_setFont(char font_nr) {
   switch(font_nr) {

Marlin/ultralcd.h

   #ifdef DOGLCD
     extern int lcd_contrast;
     void lcd_setcontrast(uint8_t value);
-    static unsigned char blink = 0; // Variable for visualization of fan rotation in GLCD
   #endif
 
   #define LCD_MESSAGEPGM(x) lcd_setstatuspgm(PSTR(x))