close update package before installing; allow remount

Close the update package before invoking the binary, to allow the
installer to unmount /cache if it wants to.  Add a function to allow
remounting of a mount as read-only.

Change-Id: Idfcc96c3da66083295177f729263560be58034e4
diff --git a/mtdutils/mtdutils.c b/mtdutils/mtdutils.c
index d16f44e..48d5ea9 100644
--- a/mtdutils/mtdutils.c
+++ b/mtdutils/mtdutils.c
@@ -455,7 +455,7 @@
             if (retry > 0) {
                 fprintf(stderr, "mtd: wrote block after %d retries\n", retry);
             }
-            fprintf(stderr, "mtd: successfully wrote block at %x\n", pos);
+            fprintf(stderr, "mtd: successfully wrote block at %llx\n", pos);
             return 0;  // Success!
         }