MXS-251: strerror

Replaces all calls to strerror with calls to strerror_r. The former
is non-thread safe while the latter is.

server/modules/protocol/maxscaled.c

@@ -380,12 +380,13 @@ int                     rc;
         } else {
             int eno = errno;
             errno = 0;
+            char errbuf[STRERROR_BUFLEN];
 	    LOGIF(LE, (skygw_log_write(
                            LOGFILE_ERROR,
                     "Failed to start listening for maxscale admin connections "
 		    "due error %d, %s\n\n",
                     eno,
-                    strerror(eno))));
+                           strerror_r(eno, errbuf, sizeof(errbuf)))));
             return 0;
         }