Added pwrite test ported by Airong Zhang.
diff --git a/runtest/syscalls b/runtest/syscalls
index ce01eea..b2e90c4 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -505,6 +505,7 @@
 pwrite01 pwrite01
 pwrite02 pwrite02
 pwrite03 pwrite03
+pwrite04 pwrite04
 
 query_module01 query_module01
 query_module02 query_module02