xenoprof: improve handling of 32-bit guests on 64-bit xen

Hi,
this patch series for xen fixes some xenoprofile type glitches between 64-bit xen and 32-bit guests, enablingthe opcontrol callgraph option to walk the call stack in both 32-bit and 64-bit guests when they are running on 64-bit xen.

The escape-code patch (3/3) should be used with a corresponding patch in the guest kernel definition of XENOPROF_ESCAPE_CODE so that both ends agree on the same escape constant value.

A few comments from my tests with oprofile 0.9.6 in userspace:
- to obtain callgraphs of the xen code, you need to enable the CONFIG_FRAME_POINTER flag during compilation of the xen binary, eg. using "make" with "frame_pointer=y".
- if the oprofiled daemon is running in a 32-bit guest, it needs to receive the xen-range in 32-bits, eg. --xen-image=/boot/xen-syms-4.1.1 --xen-range=80100000,801fe5ee

cheers,
Marcus

(1/3) xenoprof: Adjust indentation
(2/3) xenoprof: Handle 32-bit guest stacks properly in a 64-bit hypervisor (3/3) xenoprof: Make the escape code consistent across 32 and 64-bit xen