* We use 23 now as the "id" for all JSON-RPC requests.
* Every message with a different "id" can be ignored,
  as it is a request, we haven't advertised to support.
  Alternatively, we should perhaps send an error response to
  unexpected requests?
* Fixes support for the ccls server which sends window/workDoneProgress/create
  even though I didn't advertise it.
  ccls cannot practically be used with FTsymbol$ though since it returns
  full declarations.
  You can perform a fuzzy symbol search, though.

If you have projects in different languages you can set different LSPs.
The default will still come from ~/.teco_ini if you decide to set one.
The default for $SCITECO_LSP_ROOT is set by session.tes' VCS integration
based on the VCS root, but you could still overwrite it per session.

Should fix Windows builds.

* The main interface is the `FT` command.
  `FT` was an undocumented Video TECO command for etags/ctags lookups.
  I don't want to exactly copy its interface, though.
* `FT` allows looking up symbol names,
  definitions and references.
* ctags will be supported via ctags-lsp.
  LSP support is more powerful though and works without
  regenerating TAGS files all the time.
  The LSP will also allow you to customize auto-completions
  using SciTECO itself (i.e. by writing a language server
  in SciTECO).
* For multiple results, `FT$` can be used to cycle through
  results - this should mimic repeated `S$` or `N$`.
* `:FT...$` does a fuzzy search. IMHO it's not important
  to return a status integer instead. `FT` will only
  really be used in interactive mode.
* Document synchronization is supported via hooks from
  ring.c and via Scintilla notifications.
* Currently, the LSP communication is based on blocking
  GIOChannels. This means that a misbehaving hanging
  server could "lock up" the entire editor (FIXME).
  Only on ncurses you can always kill the subprocess by
  pressing CTRL+C.
  We need helper functions in spawn.c to read and write
  with interruptions.
* The textDocument/didChange notification transmits
  not only all edits, but all files' contents as well
  during initial synchronization.
  Therefore it is optimized to write and JSON-escape
  data without copying them around in memory and without
  destroying the buffer gap.
* Use $SCITECO_LSP to configure the language server.
  You can also use `tee` to capture stdin and stdout.
  Perhaps $SCITECO_LSP should be saved in .teco_session,
  so you can change it between projects?
* $SCITECO_LSP_ROOT is used to point to the project's
  root directory. session.tes will set it up automatically.

It will be useful for implementing LSP support.
It does not have JSON escape/unescape functions, so those
will still have to be written.

Source: https://github.com/rxi/sj.h

This fixes insertion of strings containing ^, ^P, ^Q, ^R, ^V, ^W, ^E.
It mainly affects Q-Register specification auto-completions, but filenames
could theoretically also contain such special characters.

* Should fix some of the Groff-rendered pages which used Unicode symbols.
* Not hotlinking to nerdfonts.com hopefully improves SEO.
  Perhaps this prevented indexing!?

* This has been broken for some time, but it didn't crash in v2.5.2.
* Even when it did not crash, the search just failed.
  In TECO-11 (judging by TECOC), we must throw an error, though.
  Video TECO on the other hand always succeeds in such cases.
* Added test case

I am unsure why it now suddenly causes problems.
pkg2appimage appears to download the appimagetool.