Add support for right-aligned roomtext

This is mostly so people making levels in an RTL language have a more
pleasant and logical experience. If roomtext is placed in a level set
to RTL, it will get p1=1, which makes that roomtext right-aligned.
Because, imagine for English you click to place roomtext, and the text
runs left of where you clicked, which wouldn't be logical.

Since it's an entity-bound property, switching RTL on and off either in
the editor or via a script does not affect existing entities.

desktop_version/src/Graphics.h

@@ -414,6 +414,8 @@ public:
     SDL_Color crewcolourreal(int t);
 
     void render_roomname(uint32_t font_flag, const char* roomname, int r, int g, int b);
+
+    void print_roomtext(int x, int y, const char* text, bool rtl);
 };
 
 #ifndef GRAPHICS_DEFINITION