Add additional parsing modes to the sequence decoder to detect and
discard unhandled sequences for ECMA-48, DEC private, and Xterm.
Add new behavior for cursor movement, cursor hiding, character deletion,
and line-wrapping.
Fix#2923
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082