Remove some variables which were set but not used.

gcc (at least as of version 4.6.0) is kind enough to point these out to us,
(when given -Wunused-but-set-variable explicitly or implicitly via -Wunused
or -Wall).

One of these cases was a legitimately unused variable. Two were simply
variables (named ignored) we were assigning only to squelch a warning about
unused function return values. I don't seem to be getting those warnings
even without setting the ignored variable. And the gcc docs. say that the
correct way to squelch that warning is with a cast to (void) anyway.

lib/message.cc

@@ -213,7 +213,6 @@ _notmuch_message_create_for_message_id (notmuch_database_t *notmuch,
 {
     notmuch_message_t *message;
     Xapian::Document doc;
-    Xapian::WritableDatabase *db;
     unsigned int doc_id;
     char *term;
 
@@ -233,7 +232,6 @@ _notmuch_message_create_for_message_id (notmuch_database_t *notmuch,
     if (notmuch->mode == NOTMUCH_DATABASE_MODE_READ_ONLY)
 	INTERNAL_ERROR ("Failure to ensure database is writable.");
 
-    db = static_cast<Xapian::WritableDatabase *> (notmuch->xapian_db);
     try {
 	doc.add_term (term, 0);
 	talloc_free (term);

notmuch-new.c

@@ -64,10 +64,9 @@ static volatile sig_atomic_t interrupted;
 static void
 handle_sigint (unused (int sig))
 {
-    ssize_t ignored;
     static char msg[] = "Stopping...         \n";
 
-    ignored = write(2, msg, sizeof(msg)-1);
+    write(2, msg, sizeof(msg)-1);
     interrupted = 1;
 }
 

notmuch-tag.c

@@ -25,10 +25,8 @@ static volatile sig_atomic_t interrupted;
 static void
 handle_sigint (unused (int sig))
 {
-    ssize_t ignored;
-
     static char msg[] = "Stopping...         \n";
-    ignored = write(2, msg, sizeof(msg)-1);
+    write(2, msg, sizeof(msg)-1);
     interrupted = 1;
 }