Fix various issues that prevented TFS running on actual HW

For one, flash memory was being decimated by all sprites being included by three different translation units. Specifying namespace on string usage should also fix compiler errors in some environments.

tfs/Makefile

@@ -14,6 +14,7 @@ OBJECTS += states/playing.o
 OBJECTS += states/gameover.o
 OBJECTS += states/tutorial.o
 OBJECTS += display/sprite.o
+OBJECTS += resources/sprites.o
 
 ###############################################################################
 # Boiler-plate

tfs/display/sprite.cpp

@@ -7,6 +7,8 @@
 
 extern Pokitto::Core game;
 
+extern const uint8_t sprites[243][258];
+
 Sprite::Sprite(
         uint8_t sprite_width,
         uint8_t sprite_height,

tfs/game.h

@@ -1,2 +1,7 @@
+#ifndef GAME_H
+#define GAME_H
+
 #define TIME_LIMIT 120000 // 2 minutes in milliseconds
 #define GAME_FRAMERATE 60
+
+#endif