FIXES:

5b47e4dc3858 #10341 security: 'modeline', 'modelineexpr'
e4ecb70d0810 #10345 Disallow API calls in the sandbox.

eval/api: don't allow the API to be called in the sandbox.

Identifying and maintaining a "secure" subset of the API would be too
much busywork. So just disable the entire thing.

Modeline fix backports

Problem:    Misspelled mkspellmem as makespellmem.
Solution:   Drop duplicate help entry, fix test. (Naruhiko Nishino, Ken
            Takata, closes vim/vim#4437)
https://github.com/vim/vim/commit/076073950c44ea0e35bc39d539dc7ab41bf9c7ec

Problem:    Error when editing test file.
Solution:   Remove part of modeline.
https://github.com/vim/vim/commit/3020a87cb121123abf1e9a1eca0eddac241fc481

Problem:    Modeline test fails with python but without pythonhome.
Solution:   Correct test argument.
https://github.com/vim/vim/commit/e09244ee3567d658c293fb1ae0d47a1a8be870ac

Problem:    can set 'modelineexpr' in modeline.
Solution:   Add P_SECURE flag.
https://github.com/vim/vim/commit/7e800c6047c8a9cc3e5cbc019a4dc91ec36616b1

Problem:    Using expressions in a modeline is unsafe.
Solution:   Disallow using expressions in a modeline, unless the
            'modelineexpr' option is set.  Update help, add more tests.
https://github.com/vim/vim/commit/110289e78195b6d01e1e6ad26ad450de476d41c1

Problem:    Modeline test with keymap still fails.
Solution:   Check that the keymap feature is available for the failure assert.
https://github.com/vim/vim/commit/3067a4dd0d768d1e4a47cf3c100f3e2b462717d7