target-i386: Broadwell CPU model

This adds a new CPU model named "Broadwell". It has all the features
from Haswell, plus PREFETCHW, RDSEED, ADX, SMAP.

PREFETCHW was already supported as "3dnowprefetch".

RDSEED, ADX was added on Linux v3.15-rc1.

SMAP was added on Linux v3.15-rc2.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Cc: Wang, Yong Y <yong.y.wang@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Dugger, Donald D <donald.d.dugger@intel.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>