Include **/*.aj files in *-sources.jar files

Previously only **/*.java sources files were included in the sources
jars. This is not ideal for the spring-aspects jar nor does it match
prior versions of the sources jars.

Now **/*.aj files are included in addition to the **/*.java files.

Issue: SPR-9576

build.gradle

@@ -71,7 +71,8 @@ configure(subprojects) { subproject ->
 
     task sourcesJar(type: Jar, dependsOn:classes) {
         classifier = 'sources'
-        from sourceSets.main.allJava
+        from sourceSets.main.allJava.srcDirs
+        include '**/*.java', '**/*.aj'
     }
 
     task javadocJar(type: Jar) {