libguile-ssh: Fix warnings

* libguile-ssh/key-type.c, libguile-ssh/message-type.c,
  libguile-ssh/server-type.c, libguile-ssh/session-type.c,
  libguile-ssh/sftp-file-type.c, libguile-ssh/sftp-session-type.c: Convert a
  converter procedure to 'converter_t' before passing to 'compare_objects'.

Author: artyom-poptsov

libguile-ssh/key-type.c

@@ -88,7 +88,7 @@ _free (SCM arg1)
 static SCM
 _equalp (SCM x1, SCM x2)
 {
-  return compare_objects(x1, x2, gssh_key_from_scm);
+  return compare_objects(x1, x2, (converter_t) gssh_key_from_scm);
 }
 
 static int

libguile-ssh/message-type.c

@@ -66,7 +66,7 @@ _print (SCM smob,  SCM port, scm_print_state *pstate)
 SCM
 _equalp (SCM x1, SCM x2)
 {
-  return compare_objects(x1, x2, _scm_to_message_data);
+  return compare_objects(x1, x2, (converter_t) _scm_to_message_data);
 }
 
 

libguile-ssh/server-type.c

@@ -54,7 +54,7 @@ _free (SCM server)
 static SCM
 _equalp (SCM x1, SCM x2)
 {
-  return compare_objects(x1, x2, gssh_server_from_scm);
+  return compare_objects(x1, x2, (converter_t) gssh_server_from_scm);
 }
 
 static int

libguile-ssh/session-type.c

@@ -60,7 +60,7 @@ _free (SCM session)
 static SCM
 _equalp (SCM x1, SCM x2)
 {
-  return compare_objects(x1, x2, gssh_session_from_scm);
+  return compare_objects(x1, x2, (converter_t) gssh_session_from_scm);
 }
 
 static int

libguile-ssh/sftp-file-type.c

@@ -130,7 +130,7 @@ ptob_input_waiting (SCM file)
 static SCM
 equalp_sftp_file (SCM x1, SCM x2)
 {
-  return compare_objects(x1, x2, gssh_sftp_file_from_scm);
+  return compare_objects(x1, x2, (converter_t) gssh_sftp_file_from_scm);
 }
 #endif
 

libguile-ssh/sftp-session-type.c

@@ -54,7 +54,7 @@ _free (SCM sftp_session)
 static SCM
 _equalp (SCM x1, SCM x2)
 {
-  return compare_objects(x1, x2, gssh_sftp_session_from_scm);
+  return compare_objects(x1, x2, (converter_t) gssh_sftp_session_from_scm);
 }
 
 /* Printing procedure. */