[ARM] 3648/1: Update struct ucontext layout for coprocessor registers

Patch from Daniel Jacobowitz

In order for userspace to find saved coprocessor registers, move them from
struct rt_sigframe into struct ucontext.  Also allow space for glibc's
sigset_t, so that userspace and kernelspace can use the same ucontext
layout.  Define the magic numbers for iWMMXt in the header file for easier
reference.  Include the size of the coprocessor data in the magic numbers.

Also define magic numbers and layout for VFP, not yet saved.

Signed-off-by: Daniel Jacobowitz <dan@codesourcery.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>