Start building against Spring Framework 4.3.8 snapshots

Closes gh-7949
See gh-8712

spring-boot-dependencies/pom.xml

@@ -145,7 +145,7 @@
 		<snakeyaml.version>1.17</snakeyaml.version>
 		<solr.version>5.5.4</solr.version>
 		<spock.version>1.0-groovy-2.4</spock.version>
-		<spring.version>4.3.7.RELEASE</spring.version>
+		<spring.version>4.3.8.BUILD-SNAPSHOT</spring.version>
 		<spring-amqp.version>1.6.8.RELEASE</spring-amqp.version>
 		<spring-cloud-connectors.version>1.2.3.RELEASE</spring-cloud-connectors.version>
 		<spring-batch.version>3.0.7.RELEASE</spring-batch.version>