fix some of the CMake syntax and correctly print the headless option

CMakeLists.txt

@@ -18,7 +18,7 @@ SET(CPACK_RESOURCE_FILE_README "${PROJECT_SOURCE_DIR}/README")
 set(CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/CMakeModules;${CMAKE_MODULE_PATH}")
 
 option(SIMGEAR_SHARED "Set to ON to build SimGear as a shared library/framework" OFF)
-option(SIMGEAR_HEADLESS "Set to ON to build SimGear with GUI/graphics support" OFF)
+option(SIMGEAR_HEADLESS "Set to ON to build SimGear without GUI/graphics support" OFF)
 option(JPEG_FACTORY "Enable JPEG-factory support" OFF)
 option(ENABLE_LIBSVN "Set to ON to build SimGear with libsvnclient support" ON)
 
@@ -53,7 +53,7 @@ set (BOOST_CXX_FLAGS "-DBOOST_MULTI_INDEX_DISABLE_SERIALIZATION -DBOOST_BIMAP_DI
 find_package(ZLIB REQUIRED)
 find_package(Threads REQUIRED)
 
-if (${SIMGEAR_HEADLESS})
+if(SIMGEAR_HEADLESS)
     message(STATUS "headlesss mode")
     set(NO_OPENSCENEGRAPH_INTERFACE 1)
 else()
@@ -61,13 +61,13 @@ else()
     find_package(OpenAL REQUIRED)
     find_package(ALUT REQUIRED)
     find_package(OpenSceneGraph 2.8.1 REQUIRED osgText osgSim osgDB osgParticle osgUtil)
-endif()
+endif(SIMGEAR_HEADLESS)
 
 if(JPEG_FACTORY)
     message(STATUS "JPEG-factory enabled")
     find_package(JPEG REQUIRED)
     include_directories(${JPEG_INCLUDE_DIR})
-endif()
+endif(JPEG_FACTORY)
 
 if(ENABLE_LIBSVN)
 	find_package(SvnClient)