Audio: Implement support for AL_EXT_double.

Signed-off-by: Squareys <Squareys@googlemail.com>

src/Magnum/Audio/Buffer.h

@@ -70,6 +70,20 @@ class Buffer {
              * @requires_al_extension extension @al_extension{EXT,float32}
              */
             StereoFloat32 = AL_FORMAT_STEREO_FLOAT32,
+
+            /**
+             * @brief 64-bit mono
+             *
+             * @requires_al_extension extension @al_extension{EXT,double}
+             */
+            MonoDouble = AL_FORMAT_MONO_DOUBLE_EXT,
+
+            /**
+             * @brief 64-bit interleaved stereo
+             *
+             * @requires_al_extension extension @al_extension{EXT,double}
+             */
+            StereoDouble = AL_FORMAT_STEREO_DOUBLE_EXT,
         };
 
         /**

src/MagnumExternal/OpenAL/extensions.h

@@ -37,6 +37,13 @@ extern "C" {
 #define AL_FORMAT_STEREO_FLOAT32                 0x10011
 #endif
 
+/* AL_EXT_double */
+#ifndef AL_EXT_double
+#define AL_EXT_double 1
+#define AL_FORMAT_MONO_DOUBLE_EXT                0x10012
+#define AL_FORMAT_STEREO_DOUBLE_EXT              0x10013
+#endif
+
 /* ALC_SOFT_HRTF */
 #ifndef ALC_SOFT_HRTF
 #define ALC_SOFT_HRTF 1