Validate asec names.

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

Bug: 12504045

(cherry picked from commit 669626096513cf741646cf18a9e8ba246d359596)

Change-Id: Ia9d04f373aa95878b2e81584c4167dc2d4aa0c78
diff --git a/VolumeManager.h b/VolumeManager.h
index 198b5a9..77fff87 100644
--- a/VolumeManager.h
+++ b/VolumeManager.h
@@ -145,6 +145,7 @@
     void readInitialState();
     bool isMountpointMounted(const char *mp);
     bool isAsecInDirectory(const char *dir, const char *asec) const;
+    bool isLegalAsecId(const char *id) const;
 };
 
 extern "C" {