Problem: The eval.txt help file is way too big.
Solution: Move the builtin function details to a separate file.
https://github.com/vim/vim/commit/1cae5a0a034d0545360387407a7a409310f1efe2
Note: Neovim-specific references to |functions| were changed to
|builtin-functions|. This included updates to:
1. test/functional/vimscript/functions_spec.lua
2. test/functional/vimscript/eval_spec.lua
3. runtime/doc/lua.txt