The sal functions osl[in|de]crementInterlockedCount() use atomic operations to
increment and decrement a counter. On all x86 platforms this is done with a
"lock xadd" prefix. "Lock" means here to lock the bus, a quite expensive
operation on pre HyperThreading Intel processors and quite uncessary if there is
only one non HT, single core processor in the system (xadd with prefix is around
8 times slower than without prefix). The new implementation checks if we are on
a single processor single core non HT machine and leaves the "lock" prefix out
in this case.