Also trim another eight bytes from vsprintf.o.  :)

Shaved around 100 bytes off vsprintf.o.  It's now 50 bytes smaller than
the old implementation and provides much more conformant semantics,
including the ability to return the number of characters that would have
been printed to the string had the buffer been big enough.  (iSCSI needs
this functionality).

stack, even if we don't yet print it out.

At some point, vsprintf() needs to be fixed up so that it can correctly
cope with limited-sized buffers (i.e. vsnprintf), long longs, and
standard format specifiers (e.g. "%04x").  We should also remove the
special types (MAC addresses and IP addresses).  This would then enable
us to use gcc's ability to type-check printf format strings.

compile, even if it won't yet be safe.

us to return proper PXE status codes, while simultaneously allowing for
more consistent error reporting (complete with verbose error messages as a
build-time option).