DDLEGACY -> DD_LEGACY_MACROS and prefer 0/1 to NO/YES for macro definitions
Print warning when DDLegacy.h gets imported
By default disable legacy macros for all but direct DDLog.h imports
Reword warning message
DDLegacy.h -> DDLegacyMacros.h
Merge pull request #424 from rivera-ernesto/legacy_checks

Legacy checks