README doesn't mention lua-c++ requirement

[ryandesign]

README doesn't mention lua-c++ requirement

[MarcusCalhoun-Lopez]

a8bc29c muddies the issue a bit.
If Lua is built with C++, surrounding the Lua headers with extern "C" { means the name mangled symbols are not found.

[thezbyg]

@ryandesign I agree that README should mention that C++ Lua library variant is required and will soon improve it.

@MarcusCalhoun-Lopez C++ Lua library can have unmangled symbols but it requires patched src/luaconf.h file (see https://sources.debian.org/patches/lua5.4/5.4.4-3/0003-extern_C.patch/). If symbols are mangled then extern "C" { will have to be removed from src/Lua.h file. Different Linux distributions do different things, but if this patch is only applied on Debian/Ubuntu then I could add a new build option to specify which type of Lua library will be linked.

Non C++ Lua library could also be used, but it would leak memory on Lua errors, because Lua uses different error handling method depending on used compiler. C version uses longjump and C++ version uses exceptions. If some C++ function expects to release allocated memory on exit from function or scope, then this release will not happen if longjump is used, because a simple jump to Lua error handling code will be performed.