SuperBuild: macro for inlude file only once

SuperBuild/CMake/External_boost.cmake

SuperBuild/CMake/External_curl.cmake

SuperBuild/CMake/External_expat.cmake

SuperBuild/CMake/External_fftw.cmake

SuperBuild/CMake/External_freetype.cmake

SuperBuild/CMake/External_gdal.cmake

SuperBuild/CMake/External_geos.cmake

SuperBuild/CMake/External_geotiff.cmake

SuperBuild/CMake/External_glew.cmake

SuperBuild/CMake/External_glfw.cmake

SuperBuild/CMake/External_glut.cmake

SuperBuild/CMake/External_itk.cmake

SuperBuild/CMake/External_jpeg.cmake

SuperBuild/CMake/External_libkml.cmake

SuperBuild/CMake/External_libsvm.cmake

SuperBuild/CMake/External_muparser.cmake

SuperBuild/CMake/External_muparserx.cmake

SuperBuild/CMake/External_mvd.cmake

SuperBuild/CMake/External_opencv.cmake

SuperBuild/CMake/External_openjpeg.cmake