Add commons-logging dependency explicitly for AJC

Previously, the dependency was indirectly included via CouchDB4j.

pom.xml

@@ -121,6 +121,12 @@
 			<groupId>commons-lang</groupId>
 			<artifactId>commons-lang</artifactId>
 		</dependency>
+		<!-- While commons-logging is not a required dependency, AJC fails without it. -->
+		<dependency>
+			<groupId>commons-logging</groupId>
+			<artifactId>commons-logging</artifactId>
+			<scope>provided</scope>
+		</dependency>
 		<!-- Spring -->
 		<dependency>
 			<groupId>org.springframework</groupId>