Option '-l' discards version sufix from file name

Like 'require', the command-line option '-l' discards an optional
version suffix (everything after an hyphen) from a file name when
creating the module name.

luaconf.h

@@ -257,6 +257,15 @@
 
 #endif
 
+
+/*
+** LUA_IGMARK is a mark to ignore all after it when building the
+** module name (e.g., used to build the luaopen_ function name).
+** Typically, the sufix after the mark is the module version,
+** as in "mod-v1.2.so".
+*/
+#define LUA_IGMARK		"-"
+
 /* }================================================================== */