tests/check/: Decide which header to include based on the userland ABI target and...

tests/check/: Decide which header to include based on the userland ABI target and not the kernel/cpu. Fix up structur...

Original commit message from CVS:
Patch by: Alexis Ballier <aballier at gentoo org>
* tests/check/gst/gstabi.c:
* tests/check/gst/struct_ppc64.h:
* tests/check/libs/libsabi.c:
* tests/check/libs/struct_ppc64.h:
Decide which header to include based on the userland ABI target
and not the kernel/cpu. Fix up structure sizes of ppc64 header
for 64-bit userland (#503590).  Might need something similar for
x86 too.