Validate asec names.

Make sure asec names only contain alphanumeric, underscores,
dots, or dashes. Don't allow double dots.

Bug: 12504045
Change-Id: I3dd0350c79327dc91a5a10d5724d85d99814e769
diff --git a/VolumeManager.h b/VolumeManager.h
index 9d69d6a..cc8958d 100644
--- a/VolumeManager.h
+++ b/VolumeManager.h
@@ -154,6 +154,7 @@
     void readInitialState();
     bool isMountpointMounted(const char *mp);
     bool isAsecInDirectory(const char *dir, const char *asec) const;
+    bool isLegalAsecId(const char *id) const;
 };
 
 extern "C" {