Fix va_start() macro compile warning on macOS

src/njsMessages.cpp

@@ -92,7 +92,7 @@ static const char *errMsg[] = {
 // error number doesn't fall within the valid error number range, an empty
 // string is returned.
 //-----------------------------------------------------------------------------
-string njsMessages::Get(njsErrorType err, ...)
+string njsMessages::Get(int err, ...)
 {
     char msg[NJS_MAX_ERROR_MSG_LEN + 1];
     va_list vlist;

src/njsMessages.h

@@ -99,7 +99,7 @@ typedef enum {
 //-----------------------------------------------------------------------------
 class njsMessages {
 public:
-    static string Get(njsErrorType err, ...);
+    static string Get(int err, ...);
 };
 
 #endif                                             /* __NJSMESSAGES_H__ */