vim-patch:8.1.1803: all builtin functions are global

Problem:    All builtin functions are global.
Solution:   Add the method call operator ->.  Implemented for a limited number
            of functions.
ac92e25a33

- Note that to *exactly* port hunk @@ -7376,18 +7444,19 from
  handle_subscript(), we need the :scriptversion patches (I have an open
  PR for those, but this patch works fine without them anyway).
- Port call_internal_func() from v7.4.2058.
- Adjust some error messages in tests, as they rely on the Blob patches.
- Add a modeline to test_method.vim.

Ignore the global_functions and base_method tables and prefer the
current GPerf implementation. Instead, add an extra base_arg field to
VimLFuncDef that holds the number of the argument to use as the base
(1-indexed, so that 0 may be used to refer to functions that cannot be
used as methods).

This also means we support using any argument as a base from the get-go,
rather than just the first (Vim includes this ability in future patches,
however).

To mark a function as usable as a method, use the "base" key as
described in eval.lua.

src/nvim/globals.h

@@ -972,6 +972,7 @@ EXTERN char_u e_write[] INIT(= N_("E80: Error while writing"));
 EXTERN char_u e_zerocount[] INIT(= N_("E939: Positive count required"));
 EXTERN char_u e_usingsid[] INIT(= N_(
     "E81: Using <SID> not in a script context"));
+EXTERN char_u e_missingparen[] INIT(= N_("E107: Missing parentheses: %s"));
 EXTERN char_u e_maxmempat[] INIT(= N_(
         "E363: pattern uses more memory than 'maxmempattern'"));
 EXTERN char_u e_emptybuf[] INIT(= N_("E749: empty buffer"));