Problem:    Terminal tests fail when using key with modifier.
Solution:   Use the modifyOtherKeys encoding when using RunVimInTerminal().

Problem:    Libvterm does not support the XTQMODKEYS request.
Solution:   Implement the XTQMODKEYS request and response.  Update the keycode
            check results.

Problem:    Cannot detect whether modifyOtherKeys is enabled.
Solution:   Use XTQMODKEYS introduced by xterm version 377 to request the
            modifyOtherKeys level.  Update the keycode check results.

Problem:    Part of making search more efficient is missing.
Solution:   Add the change in searchit().

Problem:    Eclipse preference files are not recognized.
Solution:   Add a pattern to use "jproperties" for Eclipse preference files.
            (closes #11618)

Problem:    Trying every character position for a match is inefficient.
Solution:   Use the start position of the match ignoring "\zs".

Problem:    The pattern "\_s\zs" matches at EOL.
Solution:   Make the pattern "\_s\zs" match at the start of the next line.
            (closes #11617)

Problem:    Crash when unletting a variable while listing variables.
Solution:   Disallow changing a hashtable while going over the entries.
            (closes #11435)

Problem:    'ttyfast' is set for arbitrary terminals.
Solution:   Always set 'ttyfast'. (closes #11549)

Problem:    Invalid memory access in substitute with function that goes to
            another file.
Solution:   Check for text locked in CTRL-W gf.