patch 8.2.0111: VAR_SPECIAL is also used for booleans

Problem:    VAR_SPECIAL is also used for booleans.
Solution:   Add VAR_BOOL for better type checking.
diff --git a/src/if_lua.c b/src/if_lua.c
index 9b03c97..b80b6c9 100644
--- a/src/if_lua.c
+++ b/src/if_lua.c
@@ -535,6 +535,7 @@
 	case VAR_DICT:
 	    luaV_pushdict(L, tv->vval.v_dict);
 	    break;
+	case VAR_BOOL:
 	case VAR_SPECIAL:
 	    if (tv->vval.v_number <= VVAL_TRUE)
 		lua_pushinteger(L, (int) tv->vval.v_number);
@@ -564,7 +565,7 @@
     switch (lua_type(L, pos))
     {
 	case LUA_TBOOLEAN:
-	    tv->v_type = VAR_SPECIAL;
+	    tv->v_type = VAR_BOOL;
 	    tv->vval.v_number = (varnumber_T) lua_toboolean(L, pos);
 	    break;
 	case LUA_TNIL: