Amended and retested for 32 bit "borrow ops" series

[anton.ivanov at cambridgegreys.com]

Hi All,

Apologies for sending a broken version for 32 bit.

This is an amended version which has been tested for 32 bit with/without
glibc "borrowing" and 64 bit with/without glibc borrowing.

It also includes a proper 32 bit futex implementation.

I have combined all patches and bumped the version to no 4.

The total performance difference as measured with dd on a ubd device
which is mostly cached in-memory is ~ 1.3 times for 64 bit and 2.4 times
for 32 bit.

Other benchmarks (find, boot time, etc) benefit as well, but the benefit
is not so drastic.

All tests performed on a Ryzen 5 1600X host.