Add s390 parts to common code files.

Patch history
-------------
v2->v3:

 * Add: s390: Consolidate -msoft-float into Makefile.compel
Reviewed-by: Alice Frosi <alice@linux.vnet.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>