doxygen: Enable EXTRACT_ALL so that Doxygen identifies namespaces

Doxyfile

@@ -419,7 +419,7 @@ LOOKUP_CACHE_SIZE      = 0
 # normally produced when WARNINGS is set to YES.
 # The default value is: NO.
 
-EXTRACT_ALL            = NO
+EXTRACT_ALL            = YES
 
 # If the EXTRACT_PRIVATE tag is set to YES all private members of a class will
 # be included in the documentation.