Adds method call support for all functions in the patch, but it cannot
be fully ported due to missing tests for:
- index(): requires Blobs from v8.1.0735.
Note that index() was already added as a method in v8.1.1803;
this patch only adds a test.
- iconv(): requires v8.1.1136 for test_termcodes.vim.
Nvim deprecated inputdialog(), so it no longer has an eval.txt entry.
Keep the test for hlexists() commented-out, just like previously. (Nvim
always defines the Number group, so it always returns 1 instead)
Cannot include both changes to test_syn_attr.vim as Nvim doesn't support
":hi term=..."; however, both test the same ->hlID() syntax anyway.
