Relicense files for which I am the sole author (as identified by
util/relicense.pl).

Signed-off-by: Michael Brown <mcb30@ipxe.org>

When running in a virtual machine, switching to real mode may be
expensive.  Allow interrupts to be enabled while in protected mode and
reflected down to the real-mode interrupt handlers.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Add FILE_LICENCE declarations to almost all files that make up the
various standard builds of gPXE.

The userptr_t is now the fundamental type that gets used for conversions.
For example, virt_to_phys() is implemented in terms of virt_to_user() and
user_to_phys().

advantage of the fact that we have to have a permanently-resident block
in base memory.