configure: Disable OpenAL support by default

There's apparently a new OpenAL version which contains some constructor
code that runs at startup if the binary links with OpenAL at all (even
if no OpenAL function is called). This startup code does some
nontrivial interaction with ALSA libraries and as a side effect this
idiocy also breaks test binaries run by configure, causing features to
not be detected. Avoid the problems by disabling OpenAL by default.
It's not a particularly good audio output method anyway and there are
almost certainly fewer users who would benefit from it automatically
being available than users who'd suffer from some kind of breakage
caused by it.

configure

@@ -388,7 +388,7 @@ Audio output:
   --disable-esd          disable esd audio output [autodetect]
   --disable-pulse        disable Pulseaudio audio output [autodetect]
   --disable-jack         disable JACK audio output [autodetect]
-  --disable-openal       disable OpenAL audio output [autodetect]
+  --enable-openal        enable OpenAL audio output [disable]
   --disable-nas          disable NAS audio output [autodetect]
   --disable-sgiaudio     disable SGI audio output [autodetect]
   --disable-sunaudio     disable Sun audio output [autodetect]
@@ -560,7 +560,7 @@ _esd=auto
 _pulse=auto
 _jack=auto
 _dart=auto
-_openal=auto
+_openal=no
 _libcdio=auto
 _liblzo=auto
 _mad=auto