Allow building for x86 Linux on GCC < 4.5

Signed-off-by: Giel van Schijndel <me@mortis.eu>
Sparc: use the FLUSHW instruction when available

This instruction tends to have better performance than

    ta ST_FLUSHWINDOWS

It isn't available on all systems though, hence the conditional.

Signed-off-by: Giel van Schijndel <me@mortis.eu>
Merge pr41: use FLUSHW on sparc
add Giel van Schijndel