Revert "Remove duplicated default definition for ENABLE_CONTEXT_MENU"

This reverts commit 6e469c02d50751e13dae3f858db7c46f5f6d649b.
Revert "Switch ENABLE_CONTEXT_MENUS ON by default"

This reverts commit 83dfa399ee14b3e9a457e91673d3cc45691644d9.