Upgrade Xdebug to v2.5.1

Author: rtucek

Dockerfile

@@ -15,7 +15,7 @@ LABEL \
 ENV \
     NGINX_VERSION=1.11.11 \
     PHP_VERSION=7.1.2 \
-    XDEBUG_VERSION=2.5.0 \
+    XDEBUG_VERSION=2.5.1 \
     VERSION=${VERSION}
 
 COPY \