Add spring-build 2.2.3.

spring-build was previously included via an svn:external. Adding
directly to the source tree under Git to avoid the need for a git
submodule.

In order to build from any earlier commit, it is recommended to
export spring-build or symlink an existing copy into the root
of the spring-framework project and then build normally.

$ svn export https://src.springsource.org/svn/spring-build/tags/project-build-2.2.3 spring-build

spring-build/multi-bundle/default.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project name="default-multi-bundle">
+
+	<import file="common.xml"/>
+	<import file="artifact.xml"/>
+	<import file="quality.xml"/>
+	<import file="package.xml"/>
+	<import file="publish.xml"/>
+
+</project>