Switch to the lowmem tremor branch

in addition to using slightly less memory, this branch also doesn't seem
to have the same issues with `-O2` builds that the main branch has.

lib/tremor/os.h

@@ -2,13 +2,13 @@
 #define _OS_H
 /********************************************************************
  *                                                                  *
- * THIS FILE IS PART OF THE OggVorbis 'TREMOR' CODEC SOURCE CODE.   *
+ * THIS FILE IS PART OF THE TremorOggVorbis 'TREMOR' CODEC SOURCE CODE.   *
  *                                                                  *
  * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
  * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
  * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
  *                                                                  *
- * THE OggVorbis 'TREMOR' SOURCE CODE IS (C) COPYRIGHT 1994-2002    *
+ * THE TremorOggVorbis 'TREMOR' SOURCE CODE IS (C) COPYRIGHT 1994-2002    *
  * BY THE Xiph.Org FOUNDATION http://www.xiph.org/                  *
  *                                                                  *
  ********************************************************************
@@ -18,7 +18,7 @@
  ********************************************************************/
 
 #include <math.h>
-#include <ogg/os_types.h>
+#include "os_types.h"
 
 #ifndef _V_IFDEFJAIL_H_
 #  define _V_IFDEFJAIL_H_
@@ -41,8 +41,6 @@
 #  define rint(x)   (floor((x)+0.5f)) 
 #  define NO_FLOAT_MATH_LIB
 #  define FAST_HYPOT(a, b) sqrt((a)*(a) + (b)*(b))
-#  define LITTLE_ENDIAN 1
-#  define BYTE_ORDER LITTLE_ENDIAN
 #endif
 
 #ifdef HAVE_ALLOCA_H