tools include: Fix strict-aliasing rules breakage

Vinson reported build breakage with gcc 4.4 due to strict-aliasing.

   CC       util/annotate.o
 cc1: warnings being treated as errors
 util/annotate.c: In function ‘disasm__purge’:
 linux-next/tools/include/linux/compiler.h:66: error: dereferencing
 pointer ‘res.41’ does break strict-aliasing rules

The reason is READ_ONCE/WRITE_ONCE code we took from kernel sources.  They
intentionaly break aliasing rules. While this is ok for kernel because it's
built with -fno-strict-aliasing, it breaks perf which is build with
-Wstrict-aliasing=3.

Using extra __may_alias__ type to allow aliasing in this case.

Reported-and-tested-by: Vinson Lee <[email protected]>
Signed-off-by: Jiri Olsa <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Martin Liska <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rabin Vincent <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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