* Updated AL headers

* Added a Makefile option USE_LOCAL_HEADERS which can be disabled to use system
  headers if desired

code/unix/Makefile

@@ -70,6 +70,10 @@ ifndef USE_OPENAL_DLOPEN
 USE_OPENAL_DLOPEN=0
 endif
 
+ifndef USE_LOCAL_HEADERS
+USE_LOCAL_HEADERS=1
+endif
+
 ifndef BUILD_CLIENT
 BUILD_CLIENT=1
 endif
@@ -653,6 +657,10 @@ ifdef DEFAULT_BASEDIR
   BASE_CFLAGS += -DDEFAULT_BASEDIR=\\\"$(DEFAULT_BASEDIR)\\\"
 endif
 
+ifeq ($(USE_LOCAL_HEADERS),1)
+  BASE_CFLAGS += -DUSE_LOCAL_HEADERS=1
+endif
+
 ifeq ($(GENERATE_DEPENDENCIES),1)
   ifeq ($(CC),gcc)
     DEPEND_CFLAGS=-MMD