add the alc.h header file vor OpenAL context related code

diff --git a/simgear/sound/soundmgr_openal.hxx b/simgear/sound/soundmgr_openal.hxx
index 2c40eecaf5a4e448bbd91826484598da459cb44b..84c3350289a638813c1eb2ba416649f149ad1501 100644 (file)
--- a/simgear/sound/soundmgr_openal.hxx
+++ b/simgear/sound/soundmgr_openal.hxx
@@ -45,9 +45,11 @@
 # define AL_ILLEGAL_ENUM AL_INVALID_ENUM
 # define AL_ILLEGAL_COMMAND AL_INVALID_OPERATION
 # include <OpenAL/al.h>
+# include <OpenAL/alc.h>
 # include <OpenAL/alut.h>
 #else
 # include <AL/al.h>
+# include <AL/alc.h>
 # include <AL/alut.h>
 #endif