do not add gtkdatabox+goocanvas without GTK2, fixes robotology#237

extern/CMakeLists.txt

@@ -25,7 +25,7 @@ if(YARP_USE_SQLITE AND NOT YARP_USE_SYSTEM_SQLITE)
     set(SQLite_DEFINITIONS ${SQLite_DEFINITIONS} PARENT_SCOPE)
 endif(YARP_USE_SQLITE AND NOT YARP_USE_SYSTEM_SQLITE)
 
-if(CREATE_YARPSCOPE)
+if(CREATE_YARPSCOPE AND YARP_HAS_GTK2)
     # GtkDatabox
     if(YARP_USE_GTKDATABOX AND NOT YARP_USE_SYSTEM_GTKDATABOX)
         add_subdirectory(gtkdatabox)
@@ -41,9 +41,9 @@ if(CREATE_YARPSCOPE)
         set(GtkDataboxMM_LIBRARIES ${GtkDataboxMM_LIBRARIES} PARENT_SCOPE)
         set(GtkDataboxMM_DEFINITIONS ${GtkDataboxMM_DEFINITIONS} PARENT_SCOPE)
     endif(YARP_USE_GTKDATABOXMM AND NOT YARP_USE_SYSTEM_GTKDATABOXMM)
-endif(CREATE_YARPSCOPE)
+endif()
 
-if(CREATE_GYARPBUILDER)
+if(CREATE_GYARPBUILDER AND YARP_HAS_GTK2)
     # GooCanvas
     if(YARP_USE_GOOCANVAS AND NOT YARP_USE_SYSTEM_GOOCANVAS)
         add_subdirectory(goocanvas)
@@ -59,4 +59,4 @@ if(CREATE_GYARPBUILDER)
         set(GooCanvasMM_LIBRARIES ${GooCanvasMM_LIBRARIES} PARENT_SCOPE)
         set(GooCanvasMM_DEFINITIONS ${GooCanvasMM_DEFINITIONS} PARENT_SCOPE)
     endif(YARP_USE_GOOCANVASMM AND NOT YARP_USE_SYSTEM_GOOCANVASMM)
-endif(CREATE_GYARPBUILDER)
+endif()