The patch enables the mips2 ISA for the ll/sc operations, and then restores
it when done.  The kernel/libc emulation code will take over on CPUs without
ll/sc, and on CPUs with it, it'll use the operations provided by the CPU.

Combined with the earlier fix (removing -mips2), postgresql builds again on
mips and mipsel.  The patch is against 7.2-7.

Oliver Elphick