Upgrade to Jackson 2.6.4

Closes gh-4722

spring-boot-dependencies/pom.xml

@@ -86,7 +86,7 @@
 		<httpclient.version>4.5.1</httpclient.version>
 		<httpcore.version>4.4.4</httpcore.version>
 		<infinispan.version>8.0.1.Final</infinispan.version>
-		<jackson.version>2.6.3</jackson.version>
+		<jackson.version>2.6.4</jackson.version>
 		<janino.version>2.7.8</janino.version>
 		<javassist.version>3.18.1-GA</javassist.version> <!-- Same as Hibernate -->
 		<javax-cache.version>1.0.0</javax-cache.version>