x86: break mutual header inclusion

This breaks up the mutual inclusion between headers ptrace.h and vm86.h
by moving some small part of vm86.h which is needed by ptrace.h into
processor-flags.h.

We also try to move #include lines to the top.

This has been compile tested on x86_32 and x86_64 defconfig, and run
through 'make headers_check'.

Cc: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>