musl compat cleanups
Merge branch 'cleanups'

Conflicts:
	include/sys/zfs_context.h
	lib/libspl/include/assert.h
	lib/libspl/include/rpc/xdr.h
	lib/libspl/include/sys/va_list.h
	lib/libspl/xdr.c
	module/nvpair/nvpair.c