Adapt to change in <variable> XML

Since commit ddea983ade5c2af7b1b3c5152dfc8c05984d3447 in yast-core, the
<variable> element in XML produced by ycpc does not store the namespace
as part of the "name" attribute, but in a separate "ns" attribute. This
commit adapts Y2R to that change.

Part of a fix of #8.
Adapt to change in <assign> XML

Since commit ddea983ade5c2af7b1b3c5152dfc8c05984d3447 in yast-core, the
<assign> element in XML produced by ycpc does not store the namespace as
part of the "name" attribute, but in a separate "ns" attribute. This
commit adapts Y2R to that change.

Part of a fix of #8.
Adapt to change in <builtin> XML

Since commit ddea983ade5c2af7b1b3c5152dfc8c05984d3447 in yast-core, the
<builtin> element in XML produced by ycpc does not store the namespace
as part of the "name" attribute, but in a separate "ns" attribute. This
commit adapts Y2R to that change.

Part of a fix of #8.