Fixes in build systems for autotools and cmake, see Issue 438

Thanks to Daniel KO Listas at the ODE mailing list
Don't build graphics demos when OpenGL or GLUT is not found
CMake will still build the non-graphical HelloWorld demo (output text to console)

Fix linker error: ThreadingDemo requires pthreads on UNIX systems
Thanks to reptor, see also http://bulletphysics.org/Bullet/phpBB3/posting.php?mode=reply&f=9&t=5748

Demos/ThreadingDemo/CMakeLists.txt

@@ -19,22 +19,24 @@ INCLUDE_DIRECTORIES(
 	${VECTOR_MATH_INCLUDE}
 )
 
-IF (USE_GLUT)
-	LINK_LIBRARIES(
-	OpenGLSupport  BulletMultiThreaded BulletDynamics  BulletCollision LinearMath  ${GLUT_glut_LIBRARY} ${OPENGL_gl_LIBRARY} ${OPENGL_glu_LIBRARY}
-	)
+LINK_LIBRARIES(
+BulletMultiThreaded BulletDynamics  BulletCollision LinearMath 
+)
 
-	IF (WIN32)
+IF (WIN32)
+ADD_EXECUTABLE(AppThreadingDemo
+		main.cpp
+		${BULLET_PHYSICS_SOURCE_DIR}/msvc/bullet.rc
+	)
+ELSE()
 	ADD_EXECUTABLE(AppThreadingDemo
-			main.cpp
-			${BULLET_PHYSICS_SOURCE_DIR}/msvc/bullet.rc
-		)
-	ELSE()
-		ADD_EXECUTABLE(AppThreadingDemo
-			main.cpp
-		)
-	ENDIF()
-ENDIF (USE_GLUT)
+		main.cpp
+	)
+ENDIF()
+
+IF (UNIX)
+  TARGET_LINK_LIBRARIES(AppThreadingDemo pthread)
+ENDIF(UNIX)
 
 IF (INTERNAL_ADD_POSTFIX_EXECUTABLE_NAMES)
 			SET_TARGET_PROPERTIES(AppThreadingDemo PROPERTIES  DEBUG_POSTFIX "_Debug")