will enable us to cascade async operations, which is necessary in order to
properly support DNS.  (For example, an HTTP request may have to redirect
to a new location and will have to perform a new DNS lookup, so we can't
just rely on doing the name lookup at the time of parsing the initial
URL).

Anything other than HTTP is probably broken right now; I'll fix the others
up asap.

handle something as convoluted as

  ftp://joe:secret@insecure.org:8081/hidden/path/to?what=is#this

return a static buffer.

tcpip_tx().  This avoids the irritating wait when you accidentally type
"kernel pxelinux.0" before bringing up the network interface.

Add ENETUNREACH to strerror()'s list.

retrying".

doesn't want to go to the hassle of processing a full memory map.

initrds.

Parse command line for "vga=" and "mem=" parameters

Add a path for isolinux.bin that is correct on my system; hopefully it
will work on others too.

Move pxe_boot() code to pxe_image.c

This bug found by setting read and write watchpoints at NULL in bochs.

Shut down before jumping to the multiboot image.

do it.

set_fbms() will also update the E820 hidden region.

to start on a non-page boundary.  Make life safer by rounding out our
edited regions.

Add IMAGE_PXE to use the new image format framework.  "kernel pxelinux.0"
now works.

don't overwrite the parameter block until *after* the debug code.

clue what the "previous" interrupt handler will do, which could range
from "just an iret" to "disable the interrupt"), and that means that
we have to take responsibility for ACKing all interrupts.  Joy.