Create assembler macros for saving and restoring 'struct bregs'

Create macros SAVEBREGS_POP_DSEAX and RESTOREBREGS_DSEAX for saving
and restoring the cpu state.  These are similar to the existing
PUSHBREGS and POPBREGS macros.

This also fixes a bug in __farcall16 which inadvertently restored %ds
in %es and vice-versa.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
3 files changed