Problem: tests: no support for env variables when running Vim in
terminal
Solution: support the "env" argument in RunVimInTerminal(),
close swapfiles properly in test_termcodes,
use CheckFeature in test_termencoding
Signed-off-by: Christian Brabandt <cb@256bit.org>
Problem: Various inconsistencies in test files.
Solution: Add modelines where they were missing. Use Check commands instead
of silently skipping over tests. Adjust indents and comments.
(Ken Takata, closes#6695)
