PATCH: Add x32 support to tcbhead_t

[David Miller]

From: Roland McGrath <roland@hack.frob.com>
Date: Mon, 14 May 2012 12:31:46 -0700 (PDT)

>> __attribute__ ((aligned (32))) doesn't work on field of
>> a struct.   You have to either manually pad it or use
>> an aligned type.
> 
> The GCC manual contradicts this claim.

This area is a true rats nest.

Just to give you an example, I bet you didn't know that GCC will align
variables differently if they are declared static to a compilation
unit vs. globally visible.