MFC r306681, r336249-r336250, r336261: remove inflate conflict

r306681:
ANSIfy inflate.c

Reviewed by: kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D8143

r336249:
Fix sparc64 builds

gcc is complaining about struct infate being defined in a parameter
list. It's inclear how long this has been broken, but the fix is
simple enough.

r336250:
There's two files in the sys tree named inflate.c, in addition
to it being a common name elsewhere. Rename the old kzip one
to subr_inflate.c.

This actually fixes the build issues on sparc64 that my inclusion of
.PATH ${SYSDIR}/kern created in r336244, so also revert the broken
workaround I committed in r336249.

This slipped passed me because apparently, I never did a clean build.

r336261:
Catch up to the inflate renaming.