Replace exception_print_same with operator!=

I noticed that exception_print_same is only used in a single spot, and
it seemed to be better as an operator!= method attached to
gdb_exception.

Regression tested on x86-64 Fedora 34.

gdb/exceptions.c

@@ -133,17 +133,3 @@ exception_fprintf (struct ui_file *file, const struct gdb_exception &e,
       print_exception (file, e);
     }
 }
-
-/* See exceptions.h.  */
-
-int
-exception_print_same (const struct gdb_exception &e1,
-		      const struct gdb_exception &e2)
-{
-  const char *msg1 = e1.message == nullptr ? "" : e1.what ();
-  const char *msg2 = e2.message == nullptr ? "" : e2.what ();
-
-  return (e1.reason == e2.reason
-	  && e1.error == e2.error
-	  && strcmp (msg1, msg2) == 0);
-}

gdb/exceptions.h

@@ -31,7 +31,4 @@ extern void exception_fprintf (struct ui_file *file,
 			       const char *prefix,
 			       ...) ATTRIBUTE_PRINTF (3, 4);
 
-/* Compare two exception objects for print equality.  */
-extern int exception_print_same (const struct gdb_exception &e1,
-				 const struct gdb_exception &e2);
 #endif

gdb/exec.c

@@ -201,7 +201,7 @@ try_open_exec_file (const char *exec_file_host, struct inferior *inf,
 	}
       catch (const gdb_exception_error &err)
 	{
-	  if (!exception_print_same (prev_err, err))
+	  if (prev_err != err)
 	    warning ("%s", err.what ());
 	}
     }

gdbsupport/common-exceptions.h

@@ -165,6 +165,23 @@ struct gdb_exception
     return message->c_str ();
   }
 
+  /* Compare two exceptions.  */
+  bool operator== (const gdb_exception &other) const
+  {
+    const char *msg1 = message == nullptr ? "" : what ();
+    const char *msg2 = other.message == nullptr ? "" : other.what ();
+
+    return (reason == other.reason
+	    && error == other.error
+	    && strcmp (msg1, msg2) == 0);
+  }
+
+  /* Compare two exceptions.  */
+  bool operator!= (const gdb_exception &other) const
+  {
+    return !(*this == other);
+  }
+
   enum return_reason reason;
   enum errors error;
   std::shared_ptr<std::string> message;