TEDIT feature: Quiet variant of READONLY

[rmkaplan]

In Quiet mode, when the user tries to type into the document, Tedit would simply ignore the typein without putting up a warning message in the prompt window.

This would be useful for viewing applications, like @pamoroso hex dumper. Also, DINFO man windows could be run with a Tedit process so that meta commands like meta-F (Find) etc. would go through, as in other windows.