Add libsrtp to .gitignore.

TBR=mallinath@webrtc.org

Review URL: http://webrtc-codereview.appspot.com/349004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@1379 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/.gitignore b/.gitignore
index e011861..3200e58 100644
--- a/.gitignore
+++ b/.gitignore
@@ -44,6 +44,7 @@
 /third_party/libjingle
 /third_party/libjpeg
 /third_party/libjpeg_turbo
+/third_party/libsrtp
 /third_party/libvpx
 /third_party/libyuv
 /third_party/llvm-build