2.5's signal delivery is 20% slower than 2.4.  A signal send/handle
cycle is performing a total of 24 copy_*_user() calls, and
copy_*_user() got optimised for large copies.

The patch reduces that to six copy_*_user() calls, and gets us up to
about 5% slower than 2.4.  We'd have to go back to some additional
inlined copy_user() code to get the last 3% back.  And HZ=100 to get
the 2% back.

It is noteworthy that the benchmark is not using float at all during
the body of the test, yet the kernel is still doing all that floating
point stuff.