Allow SDL_AUDIODRIVER="pulse" to do the right thing.

(We renamed this audio target at some point; the Internet didn't get the memo.)

src/audio/SDL_audio.c

@@ -577,6 +577,11 @@ SDL_AudioInit(const char *driver_name)
         driver_name = SDL_getenv("SDL_AUDIODRIVER");
     }
 
+    /* Older versions of SDL had a different name for the PulseAudio target. */
+    if (driver_name && (SDL_strcmp(driver_name, "pulse") == 0)) {
+        driver_name = "pulseaudio";
+    }
+
     for (i = 0; (!initialized) && (bootstrap[i]); ++i) {
         /* make sure we should even try this driver before doing so... */
         const AudioBootStrap *backend = bootstrap[i];