Simplification in the parameters of 'luaD_precall'

The parameters 'nresults' and 'delta1', in 'luaD_precall', were never
meaningful simultaneously. So, they were combined in a single parameter
'retdel'.

ldo.h

@@ -49,6 +49,18 @@
 	luaD_checkstackaux(L, (fsize), luaC_checkGC(L), (void)0)
 
 
+/*
+** 'luaD_precall' is used for regular calls, when it needs the
+** number of results, and in tail calls, when it needs the 'delta'
+** (correction of base for vararg functions). The argument 'retdel'
+** codes these two options. A number of results is represented by
+** itself, while a delta is represented by 'delta2retdel(delta)'
+*/
+#define delta2retdel(d) 	(-(d) + LUA_MULTRET - 1)
+#define retdel2delta(d) 	(-(d) + LUA_MULTRET - 1)
+#define isdelta(rd)	((rd) < LUA_MULTRET)
+
+
 /* type of protected functions, to be ran by 'runprotected' */
 typedef void (*Pfunc) (lua_State *L, void *ud);
 
@@ -58,8 +70,7 @@ LUAI_FUNC int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
 LUAI_FUNC void luaD_hook (lua_State *L, int event, int line,
                                         int fTransfer, int nTransfer);
 LUAI_FUNC void luaD_hookcall (lua_State *L, CallInfo *ci);
-LUAI_FUNC CallInfo *luaD_precall (lua_State *L, StkId func, int nresults,
-                                                            int delta1);
+LUAI_FUNC CallInfo *luaD_precall (lua_State *L, StkId func, int retdel);
 LUAI_FUNC void luaD_call (lua_State *L, StkId func, int nResults);
 LUAI_FUNC void luaD_callnoyield (lua_State *L, StkId func, int nResults);
 LUAI_FUNC void luaD_tryfuncTM (lua_State *L, StkId func);