MFC r270798:
Process STT_GNU_IFUNC when doing non-plt relocations.

MFC r270802:
Only do the second pass over non-plt relocations when the first pass
found IFUNCs.

Approved by:	re (gjb)
MFC r264995 (nwhitehorn):

    Add script to setup bootable CD ISOs for both BIOS and EFI systems.
    Tested and working on QEMU. Actually using this script as the regular
    image generator, like with the memstick one, will require that the
    kernel support EFI too. In particular, the following two things are
    required:
    1. vt(9) be the default console driver
    2. vt_efifb and vt_vga be able to coexist usefully in the same kernel

    One other note here is that this requires newfs_msdos and mdconfig,
    which is really ugly. NetBSD's makefs at least seems to support FAT
    now. If that actually works, it should be imported and we can get rid
    of the mdconfig mess.

Approved by:	re
Relnotes:	Yes
Sponsored by:	The FreeBSD Foundation