lib: Add two functions: notmuch_query_get_query_string and _get_sort

It can be handy to be able to query these settings from an existing
query object.

lib/notmuch.h

@@ -361,10 +361,18 @@ typedef enum {
     NOTMUCH_SORT_UNSORTED
 } notmuch_sort_t;
 
+/* Return the query_string of this query. See notmuch_query_create. */
+const char *
+notmuch_query_get_query_string (notmuch_query_t *query);
+
 /* Specify the sorting desired for this query. */
 void
 notmuch_query_set_sort (notmuch_query_t *query, notmuch_sort_t sort);
 
+/* Return the sort specified for this query. See notmuch_query_set_sort. */
+notmuch_sort_t
+notmuch_query_get_sort (notmuch_query_t *query);
+
 /* Execute a query for threads, returning a notmuch_threads_t object
  * which can be used to iterate over the results. The returned threads
  * object is owned by the query and as such, will only be valid until

lib/query.cc

@@ -70,12 +70,24 @@ notmuch_query_create (notmuch_database_t *notmuch,
     return query;
 }
 
+const char *
+notmuch_query_get_query_string (notmuch_query_t *query)
+{
+    return query->query_string;
+}
+
 void
 notmuch_query_set_sort (notmuch_query_t *query, notmuch_sort_t sort)
 {
     query->sort = sort;
 }
 
+notmuch_sort_t
+notmuch_query_get_sort (notmuch_query_t *query)
+{
+    return query->sort;
+}
+
 /* We end up having to call the destructors explicitly because we had
  * to use "placement new" in order to initialize C++ objects within a
  * block that we allocated with talloc. So C++ is making talloc