Use copy_if_different to move luajit products in the post build step to
avoid relinking of projects depending on sol2/luagit.
This is mostly relevant when building sol2 and luajit as subprojects.
— Lua 5.1, 5.2, and 5.3 seemed to have a deficiency in which the stack thread space variable (given as a lua_State*) would die before everything referencing it would be properly dead. This made holding a reference for keep-alive purposes impossible to maintain. Therefore, we retrieve the main thread to keep it alive.
- Add a flag to allow size_t(-1) and similar shenanigans (SOL_ALL_INTEGER_VALUES_FIT)
- Half-fix, but not fully, for #1183, #1072, #1038, #965
- Fix#1126
- Prepare for #1061
