Add a DECRYPTION_INFO status.

* g10/status.h (STATUS_DECRYPTION_INFO): New.
* g10/status.c (get_status_string): Add new status string.
* g10/encr-data.c: Include status.h.
(decrypt_data): Print STATUS_DECRYPTION_INFO.
--
This is  backport of commit  5667e33.

DECRYPTION_INFO <mdc_method> <sym_algo>
   Print information about the symmetric encryption algorithm and
   the MDC method.  This will be emitted even if the decryption
   fails.

g10/status.h

@@ -120,6 +120,8 @@
 
 #define STATUS_ERROR  85
 
+#define STATUS_DECRYPTION_INFO  86
+
 
 /*-- status.c --*/
 void set_status_fd ( int fd );