Change name of rwlock benchmark.

rw_lock is not easy for me to remember, so I prefer changing it to rwlock.

Change-Id: I0784acaca0c3b46c28184a77eb29ffe696f9ea07
diff --git a/benchmarks/pthread_benchmark.cpp b/benchmarks/pthread_benchmark.cpp
index 2f6572d..ad31e7e 100644
--- a/benchmarks/pthread_benchmark.cpp
+++ b/benchmarks/pthread_benchmark.cpp
@@ -121,8 +121,8 @@
   StopBenchmarkTiming();
 }
 
-BENCHMARK_NO_ARG(BM_pthread_rw_lock_read);
-void BM_pthread_rw_lock_read::Run(int iters) {
+BENCHMARK_NO_ARG(BM_pthread_rwlock_read);
+void BM_pthread_rwlock_read::Run(int iters) {
   StopBenchmarkTiming();
   pthread_rwlock_t lock;
   pthread_rwlock_init(&lock, NULL);
@@ -137,8 +137,8 @@
   pthread_rwlock_destroy(&lock);
 }
 
-BENCHMARK_NO_ARG(BM_pthread_rw_lock_write);
-void BM_pthread_rw_lock_write::Run(int iters) {
+BENCHMARK_NO_ARG(BM_pthread_rwlock_write);
+void BM_pthread_rwlock_write::Run(int iters) {
   StopBenchmarkTiming();
   pthread_rwlock_t lock;
   pthread_rwlock_init(&lock, NULL);