Fix compilation errors on Fedora 20.

peerconnection_jni.cc: syscall() comes from <unistd.h>
RTPtimeshift.cc: char* being compared to 0 instead of the atoi() of it
rtp_payload_registry_unittest.cc: avoid narrowing int to uint32.

BUG=2700
R=andrew@webrtc.org, fischman@webrtc.org, henrik.lundin@webrtc.org, henrike@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/5019004

Patch from Victor Costan <costan@gmail.com>.

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5248 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/AUTHORS b/AUTHORS
index 5fe488f..e5f2839 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -10,6 +10,7 @@
 Pali Rohar
 Robert Nagy
 Silviu Caragea <silviu.cpp@gmail.com>
+Victor Costan <costan@gmail.com>
 
 Google Inc.
 Intel Corporation