Added support for Lua 5.1, 5.2 and 5.4 (#6606)

This adds basic support for different Lua versions.

For Lua 5.2 and Lua 5.3, both the Bit32 and Compat53 Lua modules must be
installed for it to work. You can typically get these on Linux using

apt install lua-compat53 lua-bit32

For Lua 5.4, it should work as is, as it is a clean superset of Lua 5.3,
which is what the original Lua Flatbuffers supported.

tests/luatest.lua

@@ -370,4 +370,4 @@ if not result then
     print("Unable to run tests due to test framework error: ",err)
 end
 
-os.exit(result or -1)
+os.exit(result and 0 or -1)