DO NOT MERGE Retry unmounts in ext4 encryption

(cherry-picked from commit 29b54aab8ee2d08e2129832364f9b719dd17fa4e)

Bug: 18151196
Change-Id: I52ca23b2ce3adcff44bd003d4a12243a0bd6ac34
diff --git a/cryptfs.h b/cryptfs.h
index fa3d351..94684e2 100644
--- a/cryptfs.h
+++ b/cryptfs.h
@@ -26,6 +26,7 @@
  * partition.
  */
 
+#include <stdbool.h>
 #include <cutils/properties.h>
 
 /* The current cryptfs version */
@@ -208,6 +209,8 @@
 extern "C" {
 #endif
 
+  int wait_and_unmount(const char *mountpoint, bool kill);
+
   typedef int (*kdf_func)(const char *passwd, const unsigned char *salt,
                           unsigned char *ikey, void *params);