Support the FAT16 partition type in gpart(8)

PR:		kern/174714
Submitted by:	4721 at hushmail dot com
MFC after:	1 week
Fix error in r247960: actually assign the basename to match.iim_file.

Pointed out by:	avg
Pointy hat to:	dim
MFC after:	1 week
X-MFC-With:	r247960
Fix GCC build:
/usr/src/sys/modules/nvme/../../dev/nvme/nvme.c:211: warning: format '%qx' expects type 'long unsigned int', but argument 9 has type 'long long unsigned int' [-Wformat]