Make use of the *_NAME etc macros.

Replace hardwired strings at many places with new macros from config.h
and use the new strusage macro replacement feature.

* common/asshelp.c (lock_spawning) [W32]: Change the names of the spawn
sentinels.
* agent/command.c (cmd_import_key): Use asprintf to create the prompt.

common/gpgrlhelp.c

@@ -92,6 +92,6 @@ gnupg_rl_initialize (void)
                             cleanup_after_signal,
                             readline,
                             add_history);
-  rl_readline_name = "GnuPG";
+  rl_readline_name = GNUPG_NAME;
 #endif
 }