CMake policy: escape preproc defs automatically

Fix bddb8d4 with CMake >= v3.0.2.

CMakeLists.txt

@@ -29,15 +29,11 @@ if (excleve GREATER -1)
   set(ROOT_VERSION_MIN_5 "5.34.17")
 endif()
 
-### CMP0025   Compiler id for Apple Clang is now AppleClang.
-### CMP0042   MACOSX_RPATH is enabled by default.
-
-foreach(p
-  CMP0025 # CMake 3.0
-  CMP0042 # CMake 3.0
-  )
+foreach(p CMP0005  # Properly escape preprocessor definitions (v2.6, v3.0.2)
+          CMP0025  # Compiler id for Apple Clang is now AppleClang (v3.0)
+          CMP0042) # MACOSX_RPATH is enabled by default (v3.0)
   if(POLICY ${p})
-  cmake_policy(SET ${p} NEW)
+    cmake_policy(SET ${p} NEW)
   endif()
 endforeach()