Revert "Revert "Some cleanups to recovery.""

This reverts commit 8584fcf677.

This CL re-lands commit c0319b60f5.
The "stage" and "reason" variables are now declared as global by
dropping the static qualifier, because they may be used by vendor
recovery libraries.

Test: lunch aosp_angler-userdebug; mmma bootable/recovery
Test: lunch aosp_dragon-userdebug; mmma bootable/recovery

Change-Id: I252c346f450079478cff22bbff01590b8ab2e2b3

verifier.cpp

@@ -14,9 +14,11 @@
  * limitations under the License.
  */
 
+#include "verifier.h"
+
 #include <errno.h>
-#include <malloc.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include <algorithm>
@@ -31,9 +33,6 @@
 #include "common.h"
 #include "print_sha1.h"
 #include "ui.h"
-#include "verifier.h"
-
-extern RecoveryUI* ui;
 
 static constexpr size_t MiB = 1024 * 1024;