opt_netgraph in netgraph/netgraph.h?

Sometime between 5.4 RC3 and 5.4 STABLE, netgraph/netgraph.h went from version 
1.43.2.5 to 1.43.2.10. In doing so, an include of "opt_netgraph.h" was added 
to that file. This causes code including netgraph/netgraph.h, on my system, 
to fail to compile since opt_netgraph.h isn't in the include path.

When a kernel conf file doesn't have "options NETGRAPH" the generated 
opt_netgraph.h file is empty. With "options NETGRAPH" the file simply 
contains "#define NETGRAPH 1". So, either way, the file isn't hard to create 
- but I need to know where it should reside in the "_at_" hierarchy.

Does anyone (say julian_at_) know? And, just for curiousity sake, does anyone 
know which update step I probably overlooked which led to the breakage on my 
platform?