[RDY] Allow running random code on tabline clicks

[ZyX-I]

Intended for status line plugins.

Ref vim-airline/vim-airline#369.

[ZyX-I]

Note that double click will produce two function calls, so the second argument is rather useless. Fixing this is UI layer problem and out of scope of this PR. Vim has the same problem.

[dpelle]

This information → The information (or This piece of information)

"This information" is grammatically incorrect, as "information" is always plural in English.

[justinmk]

This is not needed by buffer.h directly, shouldn't the various .c file(s) add this include explicitly? ("include-what-you-use")

[ZyX-I]

This is needed by buffer.h because buffer.h.generated.h is considered to be a part of it. AFAIR it was already discussed since declarations generator does not collect needed includes.

[justinmk]

@ZyX-I This and other recent PRs failed because of luajit.org connection failures which only affected our builds (seems like they are blocking travis). Rebasing on master will fix this.

[justinmk]

A full stop (period) at the end of sentence fragments or item lists is not meaningful or useful. Does clint require it?

[ZyX-I]

I always write what can be considered sentences (absence of action is OK in Russian). Clint does not require this, but I omit a dot only in summaries (for them being taken as “topics”), and write dots otherwise.

[ZyX-I]

Ping.

[justinmk]

LGTM.

[ZyX-I]

Oh, I forgot to update vim_diff.txt. Though I think I assumed this will be picked up by Vim because *line plugins are pretty popular.

[justinmk]

Agreed. Though we will mention it elsewhere.

[justinmk]

@ZyX-I coverity found this, which appears valid:

*** CID 135004:  Null pointer dereferences  (FORWARD_NULL)
/src/nvim/screen.c: 6226 in clear_tab_page_click_defs()
6220         for (long i = 0; i < tpcd_size; i++) {
6221           if (i == 0 || tpcd[i].func != tpcd[i - 1].func) {
6222             xfree(tpcd[i].func);
6223           }
6224         }
6225       }
>>>     CID 135004:  Null pointer dereferences  (FORWARD_NULL)
>>>     Passing null pointer "tpcd" to "memset", which dereferences it.
6226       memset(tpcd, 0, (size_t) tpcd_size * sizeof(tpcd[0]));
6227     }
6228
6229     void screenclear(void)
6230     {
6231       check_for_delay(FALSE);