Use private headers from x11/tk/8.5 not installed by package.

Index: ng/Togl2.1/CMakeLists.txt
--- ng/Togl2.1/CMakeLists.txt.orig
+++ ng/Togl2.1/CMakeLists.txt
@@ -30,6 +30,10 @@ else(WIN32)
 
 endif(WIN32)
 
+target_include_directories(togl PRIVATE
+	${CMAKE_SOURCE_DIR}/../x11/tk/8.5/tk8.5.19/generic
+	${CMAKE_SOURCE_DIR}/../x11/tk/8.5/tk8.5.19/unix
+)
 target_include_directories(togl PUBLIC ${OPENGL_INCLUDE_DIR})
 target_link_libraries(togl PUBLIC ${OPENGL_LIBRARY})
 set_target_properties(togl PROPERTIES POSITION_INDEPENDENT_CODE ON )
