Make svnlite (actually libapr) work correctly on big-endian arches.

Otherwise, you would get errors similar to:

$ svn co svn://svn.freebsd.org/base/head test
A    test/lib
A    test/lib/libutil
svn: E200014: Checksum mismatch for
'/home/dim/test/lib/libutil/kinfo_getproc.3':
   expected:  0882097a545210d88edff8f63b328602
     actual:  b378eb08a0f4d4c97c513c4b17207f59

Approved by:	re (gjb, marius)

usr.bin/svn/lib/libapr/apr.h

@@ -373,7 +373,13 @@ typedef  apr_uint32_t            apr_uintptr_t;
 #endif
 
 /* Are we big endian? */
+#if _BYTE_ORDER == _LITTLE_ENDIAN
 #define APR_IS_BIGENDIAN	0
+#elif _BYTE_ORDER == _BIG_ENDIAN
+#define APR_IS_BIGENDIAN	1
+#else
+#error Unknown byte order.
+#endif
 
 /* Mechanisms to properly type numeric literals */
 #define APR_INT64_C(val) INT64_C(val)