Turning off compilation for GPU detector by default.

Compiler flag can be used to re-enable it

src/openalpr/detection/detectorcuda.cpp

@@ -20,6 +20,7 @@
 
 #include "detectorcuda.h"
 
+#if COMPILE_GPU
 
 using namespace cv;
 using namespace std;
@@ -137,4 +138,6 @@ namespace alpr
 
   }
 
-}
+}
+
+#endif