Separate the neovim completions from the vim ones, as their supported
options have diverged considerably.
Some documented options are not yet implemented, these are added but
commented out.
Closes#9535.
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Co-authored-by: Mahmoud Al-Qudsi <mqudsi@neosmart.net>
Implement completion for vim tags from any place within the source tree.
To prevent freezes on a huge tags file (e.g., on one from the Linux
kernel source tree), amount of completion lines is limited to 10000.
Note that the TAGS file (EMACS-compatible tags file) is not searched
here as it would not be used by vim anyway.
