Split time functions into rs_time.rsh header.

Change-Id: I598b0031d15749c91d11fbd37b075d0564a94dbf
diff --git a/rsContext.cpp b/rsContext.cpp
index 6a065b2..c5ee7ee 100644
--- a/rsContext.cpp
+++ b/rsContext.cpp
@@ -44,6 +44,7 @@
 uint32_t Context::gThreadTLSKeyCount = 0;
 uint32_t Context::gGLContextCount = 0;
 pthread_mutex_t Context::gInitMutex = PTHREAD_MUTEX_INITIALIZER;
+pthread_mutex_t Context::gLibMutex = PTHREAD_MUTEX_INITIALIZER;
 
 static void checkEglError(const char* op, EGLBoolean returnVal = EGL_TRUE) {
     if (returnVal != EGL_TRUE) {