Revert "text: Avoid creating a PangoAttrList we don't need"

Revert "text: Avoid creating a PangoAttrList we don't need"

This reverts commit 67c26650280ba64ff1c0318be8d848e9563ddb21.

The splicing we do here has the important side-effect
of shifting the preedit attributes to the right position.
Without it, we end up always underlining the first chars
in the entry, regardless where the preedit happens.