Fixed build failure on Mac OS X.
+ wimunmount now provides the '--new-image' option to cause changes to a
+ read-write mounted image to be committed as a new image rather than as
+ an update of the same image. (The corresponding new library flag is
+ WIMLIB_UNMOUNT_FLAG_NEW_IMAGE.)
+
The LZMS compression chunk size, or "dictionary size", may now be up to
1 GiB (2^30).