Try to avoid future problems caused by implicit section flags and/or
type information by instituting a policy that all .section
declarations must explicitly state the flags and type.

Most of this change was achieved using

    perl -pi \
      -e 's/".text"$/".text", "ax", \@progbits/ ; ' \
      -e 's/".text16"$/".text16", "ax", \@progbits/ ; ' \
      -e 's/".text16.null"$/".text16.null", "ax", \@progbits/ ; ' \
      -e 's/".text16.data"$/".text16.data", "aw", \@progbits/ ; ' \
      -e 's/".data"$/".data", "aw", \@progbits/ ; ' \
      -e 's/".data16"$/".data16", "aw", \@progbits/ ; ' \
      -e 's/".bss"$/".bss", "aw", \@nobits/ ; ' \
      -e 's/".bss16"$/".bss16", "aw", \@nobits/ ; ' \
      -e 's/".prefix"$/".prefix", "ax", \@progbits/ ; ' \
      -e 's/".prefix.lib"$/".prefix.lib", "awx", \@progbits/ ; ' \
      -e 's/".prefix.data"$/".prefix.data", "aw", \@progbits/ ; ' \
      -e 's/".weak"$/".weak", "a", \@nobits/ ; ' \
      `git grep -l '\.section'`

Code paths that automatically allocate memory from the FBMS at 40:13
should also free it, if possible.

Freeing this memory will not be possible if either

  1. The FBMS has been modified since our allocation, or

  2. We have not been able to unhook one or more BIOS interrupt vectors.

This allows multiple gPXE ROMs in a system to be disambiguated at boot
time; the PCI ID will show up in the boot menu for a BBS-compliant BIOS.

Move the printing functions from pxeprefix.S into libprefix.S, so they
are available for debug from any prefix.

clean separation between loading and starting, but does mean that more
PXE stacks survive the process.

addresses if the signature checks fail.

we can never return to the PXE stack and must always use INT 18.

Record all information required for populating a struct undi_device.

Make debugging output more human-readable.

and call UNDI_SHUTDOWN first to make sure the NIC is in a safe state.

memory (unless we get an error while stopping the base code).  Leave UNDI
resident (though stopped) for .kpxe.

Still need to add code to record the device identification parameters
prior to stopping UNDI.

mechanism has changed anyway, and so must be rewritten, but at least doing
this makes the output of "make symcheck" more legible.