let the "firmware" command take the file straight from the package

To do a firmware-install-on-reboot, the update binary tells recovery
what file to install before rebooting.  Let this file be specified as
"PACKAGE:<foo>" to indicate taking the file out of the OTA package,
avoiding an extra copy to /tmp.  Bump the API version number to
reflect this change.
diff --git a/recovery.c b/recovery.c
index 188d4de..5ccd38f 100644
--- a/recovery.c
+++ b/recovery.c
@@ -287,7 +287,8 @@
 static void
 prompt_and_wait()
 {
-    char* headers[] = { "Android system recovery utility",
+    char* headers[] = { "Android system recovery <"
+                          EXPAND(RECOVERY_API_VERSION) ">",
                         "",
                         "Use trackball to highlight;",
                         "click to select.",