r362666 breaking buildworld (don't know how to make nvpair.c) & Fix/Patch

[Neel Chauhan]

Hi,

When I attempt to build world in 13-CURRENT, I get this error:

===> lib/libnv (obj,includes,all,install)
[Creating objdir 
/usr/obj/usr/src/amd64.amd64/tmp/obj-tools/lib/libnv...]
make[3]: make[3]: don't know how to make nvpair.c. Stop

make[3]: stopped in /usr/src/lib/libnv
*** [legacy] Error code 2

make[2]: stopped in /usr/src
1 error

make[2]: stopped in /usr/src
*** [_legacy] Error code 2

make[1]: stopped in /usr/src
1 error

make[1]: stopped in /usr/src
*** [buildworld] Error code 2

make: stopped in /usr/src
1 error

make: stopped in /usr/src
root at omen:/usr/src #

The build broke with mmacy@'s commit r362666 which renamed nvpair.c to 
bsd_nvpair.c without renaming the Makefile.

Is anyone else having this error?

I have a patch to unbreak the build here: 
https://reviews.freebsd.org/D25481

Does the patch work?

Best,

Neel Chauhan