Allow paths to be passed to environment variables of exec task.

Example usage
  <target name="exectest">
      <exec command="exectest.bat" dir=".">
        <env key="ANT_TEST" path="../test:../test2"/>
      </exec>
  </target>


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@267839 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/types/Environment.java

@@ -76,9 +76,15 @@ public class Environment {
         public void setKey(String key) {
             this.key = key;
         }
+        
         public void setValue(String value) {
             this.value = value;
         }
+        
+        public void setPath(Path path) {
+            this.value = path.toString();
+        }
+
         public String getContent() throws BuildException {
             if (key == null || value == null) {
                 throw new BuildException("key and value must be specified for environment variables.");