Switch to g_ for globals.

That's what the Google style guide recommends, and we're starting
to get a mix.

Change-Id: Ib0c53a890bb5deed5c679e887541a715faea91fc
diff --git a/libc/bionic/thread_atexit.cpp b/libc/bionic/thread_atexit.cpp
index cad65d3..68c119d 100644
--- a/libc/bionic/thread_atexit.cpp
+++ b/libc/bionic/thread_atexit.cpp
@@ -30,7 +30,7 @@
 
 #include <pthread.h>
 
-static pthread_mutex_t gAtExitLock = PTHREAD_MUTEX_INITIALIZER;
+static pthread_mutex_t g_atexit_lock = PTHREAD_MUTEX_INITIALIZER;
 
 __BEGIN_DECLS
 __LIBC_HIDDEN__ void _thread_atexit_lock();
@@ -38,9 +38,9 @@
 __END_DECLS
 
 void _thread_atexit_lock() {
-  pthread_mutex_lock(&gAtExitLock);
+  pthread_mutex_lock(&g_atexit_lock);
 }
 
 void _thread_atexit_unlock() {
-  pthread_mutex_unlock(&gAtExitLock);
+  pthread_mutex_unlock(&g_atexit_lock);
 }