patch 7.4.1154
Problem:    No support for JSON.
Solution:   Add jsonencode() and jsondecode().  Also add v:false, v:true,
            v:null and v:none.
diff --git a/src/if_lua.c b/src/if_lua.c
index 46f881a..1c8512f 100644
--- a/src/if_lua.c
+++ b/src/if_lua.c
@@ -499,6 +499,12 @@
 	case VAR_DICT:
 	    luaV_pushdict(L, tv->vval.v_dict);
 	    break;
+	case VAR_SPECIAL:
+	    if (tv->vval.v_number <= VVAL_TRUE)
+		lua_pushinteger(L, (int) tv->vval.v_number);
+	    else
+		lua_pushnil(L);
+	    break;
 	default:
 	    lua_pushnil(L);
     }
@@ -510,7 +516,7 @@
 {
     switch(lua_type(L, pos)) {
 	case LUA_TBOOLEAN:
-	    tv->v_type = VAR_NUMBER;
+	    tv->v_type = VAR_SPECIAL;
 	    tv->vval.v_number = (varnumber_T) lua_toboolean(L, pos);
 	    break;
 	case LUA_TSTRING: