Make expand_buffer() a non-inline function, so that we can add debug
messages.

Expandable buffers now don't *always* round up to the next power of two.
This allows e.g. loading a 137MB ISO image on a machine with only 256MB
RAM...

optimise these down to the correct single "roll"/"rorl" instruction.

value.

to avoid drops even on slow NICs.

is now gPXE-specific.  (The standard malloc() et al have been in stdlib.h
for a while).

Add free memory counter.

anyone?

other protocol won't work at the moment.

protocols by URI scheme.

Tidy up code

reflect the fact that they allocate and deallocate user memory (i.e.
things reached through a userptr_t).

of blocking on asynchronous operations, when that isn't an important
aspect of the code.

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

do it.

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

that switches from line-oriented to byte-oriented partway through, such as
HTTP.

order so we can just use buffer->fill.

took out the contract to eventually call efree() when it called fetch().

Maintain the most recently loaded image at the start of the list, so that
imgautoselect() will pick it.

after a call to load().

returns the allocated buffer.