Some cleanups to recovery.

- Remove the duplicate gCurrentUI variable in recovery.cpp;
- Refactor the load/save of locale functions;
- Clean up ui_print() to get rid of 256-byte buffer limit;
- Declare ui in common.h;
- Move the typedef of Volume into roots.h.

Test: Build and boot into recovery image.

Change-Id: Ia28c116858ca754133127a5ff9c722af67ad55b7
diff --git a/roots.h b/roots.h
index a14b7d9..542f03b 100644
--- a/roots.h
+++ b/roots.h
@@ -17,7 +17,7 @@
 #ifndef RECOVERY_ROOTS_H_
 #define RECOVERY_ROOTS_H_
 
-#include "common.h"
+typedef struct fstab_rec Volume;
 
 // Load and parse volume data from /etc/recovery.fstab.
 void load_volume_table();