make sure splash start and end markers have correct position

Compiler can change position of start/end splash markers or even optimize-out
them completely, because they are not used in the fw. 
Make them part of the splash data block, so their possition is always correct.
util/xbm2lbm was changed together with other c "images" to make it consitent.

src/lcd.cpp

@@ -20,8 +20,14 @@
  */
 
 #include "lcd.h"
+
+const pm_uchar font[] PROGMEM = {
 #include "font.lbm"
+};
+
+const pm_uchar font_dblsize[] PROGMEM = {
 #include "font_dblsize.lbm"
+};
 
 #define font_5x8_x20_x7f (font+2)
 #define font_10x16_x20_x7f (font_dblsize+2)