make source archive expand to a different directory than the binary archive.

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/pool/branches/1_3_RELEASE_BRANCH@387381 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/project.properties b/project.properties
index 8195db3..a328126 100644
--- a/project.properties
+++ b/project.properties
@@ -42,6 +42,8 @@
 maven.compile.source=1.3
 maven.compile.target=1.3
 
+maven.dist.src.assembly.dir=${maven.dist.assembly.dir}/src/${maven.final.name}-src
+
 maven.jdiff.new.tag=CURRENT
 maven.jdiff.old.tag=POOL_1_2