Older Lua versions no longer compile under current gcc

[Dirk Laurie <dirk.laurie@...>]

Lua versions frm 1.1 to 2.5 do not compile on
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.5) 5.4.0 20160609.

Interestingly, Lua 1.0 compiles.

E.g. 1.1 creates the .o files but fails at the ld stage:

ld: warning: cannot find entry symbol _start; defaulting to 00000000004000f0

and 2.4 fails here:

iolib.c:19:17: error: initializer element is not constant
 static FILE *in=stdin, *out=stdout;

Maybe just some CFLAGS that one could set in the Makefile?