cmake: drop global INCLUDE_DIRECTORIES variable

It doesn't seem to be used anywhere and using this wide include might hide issues if some include actually doesn't reach some target.

cmake/CMakeLists.txt

@@ -489,7 +489,7 @@ else()
     endif()
 endif(MSVC)
 
-include_directories(${INCLUDE_DIRECTORIES}
+include_directories(
 	${Boost_INCLUDE_DIRS}
     ${CGAL_INCLUDE_DIR} ${GMP_INCLUDE_DIR} ${MPFR_INCLUDE_DIR}
 )

src/ifcmax/CMakeLists.txt

@@ -35,7 +35,6 @@ if(HAS_MAX)
         message(STATUS "Building IFCMax library for Autodesk 3ds Max SDK ${max_year}")
 
         include_directories(
-            ${INCLUDE_DIRECTORIES}
             ${OPENCOLLADA_INCLUDE_DIRS}
             ${ICU_INCLUDE_DIR}
             ${Boost_INCLUDE_DIRS}