target-i386: Register aliases for feature names with underscores

target-i386: Register aliases for feature names with underscores

Registering the actual names containing underscores as aliases
will allow management software to be aware that the old
compatibility names are suported, and will make feat2prop() calls
unnecessary when using feature names.

Also, this will help us avoid making the code support underscores
on feature names that never had them in the first place. e.g.
"+tsc_deadline" was never supported and doesn't need to be
translated to "+tsc-deadline".

In other word: this will require less magic translation of
strings, and simple 1:1 match between the config options and
actual QOM properties.

Note that the underscores are still present in the
FeatureWordInfo::feat_names arrays, because
add_flagname_to_bitmaps() needs them to be kept. The next patches
will remove add_flagname_to_bitmaps() and will allow us to
finally remove the aliases from feat_names.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>