Enhance the guest state effects notation on IRDirty calls, so as to be

Enhance the guest state effects notation on IRDirty calls, so as to be
able to describe accesses to arrays of non-consecutive guest state
sections.  This is needed to describe the behaviour of FXSAVE and
FXRSTOR in an environment where we also support AVX.

The IRDirty struct has got smaller (112 bytes vs 136 before, for a 64
bit target) whilst holding more information.

The new facility is then used to describe said FXSAVE and FXRSTOR on
amd64.  For x86 there is no change since we don't model AVX state for
x86.

git-svn-id: svn://svn.valgrind.org/vex/trunk@2362