Editing /usr/include/*.h?

[Kevin A. Pieckiel]

I want to modify sys/param.h to increase the value of MAXLOGNAME.  I know
I'll need to recompile world/kernel after such a change.  Do I need to
only modify /usr/src/sys/sys/param.h, or rather do I need to modify
/usr/include/sys/param.h?  I'm assuming when I make buildworld or make
buildkernel, the includes in /usr/include aren't used, so the latter
change will actually be overwritten when I do a make installworld.

Thanks,
Kevin