Update GDBPatternMatching test for older GDBs.

Over the years GDB is showing more registers than before.  When the
GDBPatternMatching tests were first written, some random registers were
used.  This update uses registers that are available for both old and
new gdb versions, as well as 32bit and 64bit architectures.

Change-Id: Ibbbd50d240f295e1a745fae217013f21aeabff8a
Signed-off-by: Marc Khouzam <marc.khouzam@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/38736
Tested-by: Hudson CI
Run all tests suites

Change-Id: Ie45cd924046438903c0305a70c8663f7e76a5e31