Merge branch '5.1.x'

Author: jhoeller

build.gradle

@@ -41,7 +41,7 @@ ext {
 	reactorVersion       = "Californium-SR5"
 	rxjavaVersion        = "1.3.8"
 	rxjavaAdapterVersion = "1.2.1"
-	rxjava2Version       = "2.2.6"
+	rxjava2Version       = "2.2.7"
 	slf4jVersion         = "1.7.25"	  // spring-jcl + consistent 3rd party deps
 	tiles3Version        = "3.0.8"
 	tomcatVersion        = "9.0.16"
@@ -141,7 +141,7 @@ configure(allprojects) { project ->
 	}
 
 	checkstyle {
-		toolVersion = "8.17"
+		toolVersion = "8.18"
 		configDir = rootProject.file("src/checkstyle")
 	}