fastuidraw/painter/stroked_path: prevent overdraw from arc-dashed cappers.
fastuidraw/painter/stroked_path: prevent overdraw from arc-dashed cappers.

Give each arc-dashed capper its own depth value ins stroking; this
prevents them from causing overdraw.

Change-Id: I4901a4435b9c66f85401a540fdc58ed1b7d4eb5a

01org/fastuidraw,01org/fastuidraw