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/configure.ac b/configure.ac
index bf8ef6d..320c250 100644
--- a/configure.ac
+++ b/configure.ac
@@ -311,6 +311,14 @@
   AX_SIGNED_RIGHT_SHIFT
 fi
 
+dnl autoscan thinks we need this macro because we have a member function
+dnl called "error".  Invoke the macro but don't run the check so autoscan
+dnl thinks we are in the clear.  It's highly unlikely that we will ever
+dnl actually use the function that this checks for.
+if false ; then
+  AC_FUNC_ERROR_AT_LINE
+fi
+
 AX_THRIFT_GEN(cpp, [C++], yes)
 AM_CONDITIONAL([THRIFT_GEN_cpp], [test "$ax_thrift_gen_cpp" = "yes"])
 AX_THRIFT_GEN(java, [Java], yes)