THRIFT-923. cpp: Implement a fully nonblocking server and client

There are three major parts of this:
1/ New callback-style interfaces for for a few key Thrift components:
   TAsyncProcessor for servers and TAsyncChannel for clients.
2/ Concrete implementations of TAsyncChannel and a server for
   TAsyncProcessor based on evhttp.
3/ Async-style code generation for C++

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@1005127 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/contrib/async-test/aggr.thrift b/contrib/async-test/aggr.thrift
new file mode 100644
index 0000000..c016a65
--- /dev/null
+++ b/contrib/async-test/aggr.thrift
@@ -0,0 +1,8 @@
+exception Error {
+  1: string desc;
+}
+
+service Aggr {
+  void addValue(1: i32 value);
+  list<i32> getValues() throws (1: Error err);
+}