Log Message:
vttest: Update to 20200920

20200920
	+ add test for xterm's 1016 pixel-coordinates mouse-mode.

	+ add "-q" option to display only the most recent part of a response,
	  e.g., for any-event mouse tests.

	+ remove obsolete MANIFEST, dist, dist-shar makefile targets, since
	  those are done by external scripts.

	+ use makefile ".PHONY" feature if available.

	+ updated/improved configure macros, i.e., for compiler-warnings

	+ update config.guess, config.sub