(svn r1853) Move spritecache function declarations into a header of their own and use SpriteID as parameter type where appropriate

spritecache.h

@@ -0,0 +1,16 @@
+#ifndef SPRITECACHE_H
+#define SPRITECACHE_H
+
+typedef struct {
+	int xoffs, yoffs;
+	int xsize, ysize;
+} SpriteDimension;
+
+const SpriteDimension *GetSpriteDimension(SpriteID sprite);
+byte *GetSpritePtr(SpriteID sprite);
+
+void GfxInitSpriteMem(byte *ptr, uint32 size);
+void GfxLoadSprites(void);
+void IncreaseSpriteLRU(void);
+
+#endif