Fix doxygen

Author: svekars

docs/source/Doxyfile

@@ -2415,7 +2415,8 @@ INCLUDE_FILE_PATTERNS  =
 # recursively expanded use the := operator instead of the = operator.
 # This tag requires that the tag ENABLE_PREPROCESSING is set to YES.
 
-PREDEFINED             =
+PREDEFINED += ET_NODISCARD=
+PREDEFINED += ET_DEPRECATED=
 
 # If the MACRO_EXPANSION and EXPAND_ONLY_PREDEF tags are set to YES then this
 # tag can be used to specify a list of macro names that should be expanded. The