Update glcdfont.c

glcdfont.c

@@ -6,7 +6,7 @@
 
 // standard ascii 5x7 font
 
-static unsigned char  font[] PROGMEM = {
+const static unsigned char  font[] PROGMEM = {
         0x00, 0x00, 0x00, 0x00, 0x00,   
 	0x3E, 0x5B, 0x4F, 0x5B, 0x3E, 	
 	0x3E, 0x6B, 0x4F, 0x6B, 0x3E,