Require aopalliance dependency for spring-aop

A recent commit made aopalliance optional for spring-aop, while
continuing to require it for spring-tx. On review, this is probably
overly aggressive, and for convenience aopalliance should remain
required for spring-aop. There are use cases for which aopalliance is
indeed optional, but core functionality such as <aop:scoped-proxy>
should never result in a ClassNotFoundException.

This commit returns the aopalliance dependency for spring-aop to
required status, and also explicitly notes the same dependency in other
modules that compile directly against aopalliance types.

Issue: SPR-9501

Author: cbeams

build.gradle

@@ -168,8 +168,8 @@ project('spring-aop') {
     dependencies {
         compile project(":spring-core")
         compile project(":spring-beans")
+        compile("aopalliance:aopalliance:1.0")
         compile("com.jamonapi:jamon:2.4", optional)
-        compile("aopalliance:aopalliance:1.0", optional)
         compile("commons-pool:commons-pool:1.5.3", optional)
     }
 }
@@ -248,9 +248,9 @@ project('spring-tx') {
         compile(project(":spring-aop"), optional)
         compile project(":spring-beans")
         compile project(":spring-core")
+        compile("aopalliance:aopalliance:1.0")
         compile("com.ibm.websphere:uow:6.0.2.17", provided)
         compile("javax.resource:connector-api:1.5", optional)
-        compile "aopalliance:aopalliance:1.0" // NOT optional, as opposed to in :spring-aop
         compile("org.apache.geronimo.specs:geronimo-jta_1.1_spec:1.1", optional)
         testCompile "org.easymock:easymockclassextension:2.3"
     }
@@ -287,6 +287,7 @@ project('spring-jms') {
         compile project(":spring-context")
         compile project(":spring-tx")
         compile(project(":spring-oxm"), optional)
+        compile("aopalliance:aopalliance:1.0")
         compile("org.codehaus.jackson:jackson-mapper-asl:1.4.2", optional)
     }
 }
@@ -346,6 +347,7 @@ project('spring-web') {
         compile project(":spring-aop") // for JaxWsPortProxyFactoryBean
         compile project(":spring-context")
         compile(project(":spring-oxm"), optional) // for MarshallingHttpMessageConverter
+        compile("aopalliance:aopalliance:1.0")
         compile("com.caucho:hessian:3.2.1", optional)
         compile("rome:rome:1.0", optional)
         compile("javax.el:el-api:1.0", optional)
@@ -378,6 +380,7 @@ project('spring-orm') {
     dependencies {
         // compiling against both hibernate 3 and 4 here in order to support
         // our respective orm.hibernate3 and orm.hibernate4 packages
+        compile("aopalliance:aopalliance:1.0")
         compile("org.hibernate:com.springsource.org.hibernate:3.3.1.GA", optional)
         compile("org.hibernate:hibernate-core:4.1.0.Final", optional)
         compile("org.hibernate:hibernate-cglib-repack:2.1_3", optional)