Replace setblockcolour() argument with const char*

There's no reason it needs to be an std::string here.

Although, realistically, we should be using an enum instead of
string-typing, but, eh, that can be fixed later.

desktop_version/src/BlockV.h

@@ -12,7 +12,7 @@ public:
 
     void rectset(const int xi, const int yi, const int wi, const int hi);
 
-    void setblockcolour(std::string col);
+    void setblockcolour(const char* col);
 public:
     //Fundamentals
     SDL_Rect rect;