Corrected #include directives of openal headers for MSVC.

code/client/qal.h

@@ -37,8 +37,14 @@ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 #include "../AL/al.h"
 #include "../AL/alc.h"
 #else
-#include <AL/al.h>
-#include <AL/alc.h>
+#ifdef _MSC_VER
+  // MSVC users must install the OpenAL SDK which doesn't use the AL/*.h scheme.
+  #include <al.h>
+  #include <alc.h>
+#else
+  #include <AL/al.h>
+  #include <AL/alc.h>
+#endif
 #endif
 
 #if USE_OPENAL_DLOPEN