soundlib selection in config file wasn't working

When there was more than one option #define'd
selection was not working correctly.

src/options.c

@@ -3741,8 +3741,11 @@ optfn_soundlib(
          */
         if ((op = string_for_env_opt(allopt[optidx].name, opts, FALSE))
             != empty_optstr) {
+            enum soundlib_ids option_id;
 
             get_soundlib_name(soundlibbuf, WINTYPELEN);
+            option_id = soundlib_id_from_opt(op);
+            gc.chosen_soundlib = option_id;
             assign_soundlib(gc.chosen_soundlib);
         } else
             return optn_err;

src/sounds.c

@@ -1879,6 +1879,21 @@ get_soundlib_name(char *dest, int maxlen)
     *dest = '\0';
 }
 
+enum soundlib_ids
+soundlib_id_from_opt(char *op)
+{
+    int idx;
+    struct sound_procs *defproc = &nosound_procs,
+                       *sp = 0;
+
+    for (idx = 0; idx < SIZE(soundlib_choices); ++idx) {
+        sp = soundlib_choices[idx].sndprocs;
+        if (!strcmp(sp->soundname, op))
+            return sp->soundlib_id;
+    }
+    return defproc->soundlib_id;
+}
+
 /*
  * The default sound interface
  *