upgrade header files to Lua 5.4

[takase1121]

Old header. New Lua. Me compile no work.

Updated the function prototypes, macros and structures to Lua 5.4.
Polyfills for backward compatibility with other Lua versions are removed.
lite_xl_plugin_init is now extern so that dlls with multiple entrypoints (eventually) can use it.

I've tested this new header with cffi-lua and ltreesitter.
No warnings.

Requires #1440.

[takase1121]

I haven't exported more symbols from Lite XL side yet. I would do it in another PR. If you want it here, please tell me.

[jgmdev]

Will give this a proper test later with some native plugins and see how it rolls

[jgmdev]

Tested by compiling the thread plugin and got a bunch of errors like this:

FAILED: thread.so.p/src_thread.c.o 
ccache cc -Ithread.so.p -I. -I.. -I../src -I/usr/include/SDL2 -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -std=c11 -O3 -fPIC -D_REENTRANT -DSDL_MAIN_HANDLED -MD -MQ thread.so.p/src_thread.c.o -MF thread.so.p/src_thread.c.o.d -o thread.so.p/src_thread.c.o -c ../src/thread.c
In file included from ../src/channel.h:8,
                 from ../src/thread.c:24:
../lite_xl_plugin_api.h:56:42: error: ISO C requires a named argument before ‘...’
   56 |     static ret __lite_xl_fallback_##name(...) { \
      |                                          ^~~
../lite_xl_plugin_api.h:993:1: note: in expansion of macro ‘SYMBOL_DECLARE’
  993 | SYMBOL_DECLARE(lua_State *, lua_newstate, lua_Alloc f, void *ud)
      | ^~~~~~~~~~~~~~
../lite_xl_plugin_api.h:56:42: error: ISO C requires a named argument before ‘...’
   56 |     static ret __lite_xl_fallback_##name(...) { \
      |                                          ^~~
../lite_xl_plugin_api.h:994:1: note: in expansion of macro ‘SYMBOL_DECLARE’
  994 | SYMBOL_DECLARE(void,        lua_close, lua_State *L)
      | ^~~~~~~~~~~~~~
../lite_xl_plugin_api.h:56:42: error: ISO C requires a named argument before ‘...’
   56 |     static ret __lite_xl_fallback_##name(...) { \
      |                                          ^~~
../lite_xl_plugin_api.h:995:1: note: in expansion of macro ‘SYMBOL_DECLARE’
  995 | SYMBOL_DECLARE(lua_State *, lua_newthread, lua_State *L)
      | ^~~~~~~~~~~~~~
../lite_xl_plugin_api.h:56:42: error: ISO C requires a named argument before ‘...’
   56 |     static ret __lite_xl_fallback_##name(...) { \
      |                                          ^~~

[takase1121]

@jgmdev can you retry?

The fix should work on GCC and clang. Not sure about MSVC yet.

[jgmdev]

Tested with threads and encodings and now compiled without issues, lets merge this for now, any other fixes can be worked on another PR.