Thrift: Compile without libevent.

Summary:
- Totally re-did the libevent check.
- Thrift now compiles and instals cleanly without libevent.
- (libevent is still needed to build libthriftnb.)

Reviewed By: mcslee

Test Plan:
- Ran configure and make in various configurations in my VMware.
- Clean build and install of Thrift on devrs004 (into /tmp).

Revert Plan: ok


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665267 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/cpp/configure.ac b/lib/cpp/configure.ac
index 0208f1b..5e33617 100644
--- a/lib/cpp/configure.ac
+++ b/lib/cpp/configure.ac
@@ -68,7 +68,8 @@
 
 AX_BOOST_BASE([1.33.1])
 
-AX_EVENT_BASE([1.2.0])
+AX_LIB_EVENT([1.0])
+AM_CONDITIONAL([AMX_HAVE_LIBEVENT], [test "$success" = "yes"])
 
 AC_CHECK_LIB(pthread, pthread_create)