Paragraph::Remove() Keep last remaining span as empty span.
Fix clip_to_picture test app

* We want the text to be drawn on the clipping bitmap with alpha
blending, to get an useful mask.
Add missing pipe character in KDL keymap.

For non-US keyboards, the extra 102th/105th key is used to reach \. But,
we also need it to report | when shifted (this is the key left to
"enter").

This affects only USB keyboards. Thanks to gordoncjp for reporting!