Include RootMacros.cmake in ROOTConfig.cmake

This makes ROOT's CMake macros like ROOT_GENERATE_DICTIONARY()
readily available after a successful call to find_package(ROOT),
without having to call include(${ROOT_USE_FILE}), which will
append ROOT's compilation flags to flags of the including project,
potentially overriding them (i.e. -O3 with -O2, etc).

cmake/scripts/ROOTConfig.cmake.in

@@ -61,6 +61,10 @@ get_filename_component(_thisdir "${CMAKE_CURRENT_LIST_FILE}" PATH)
 @ROOT_LIBRARY_DIR_SETUP@
 @ROOT_BINARY_DIR_SETUP@
 
+#----------------------------------------------------------------------------
+# Include RootMacros.cmake to get ROOT's CMake macros
+include(@ROOT_MODULE_PATH@/RootMacros.cmake)
+
 #----------------------------------------------------------------------------
 # Include the file listing all the imported targets and options
 if(NOT CMAKE_PROJECT_NAME STREQUAL ROOT)