vt: Fix contents of paste buffer for newcons.

Trim all word separators from end of line, except for last line and
only use '\r' to terminate the pasted lines as expected by TTY.

Submitted by: Ivan Quitschal <tezeka@hotmail.com>
Differential Revision: https://reviews.freebsd.org/D35552
PR: 263084
MFC after: 1 week
Sponsored by: NVIDIA Networking