Although libewf version 2 is still in alpha version. With this tracker the changes necessary for version 2 API support with backwards compatibility for current stable of libewf. The patch only changes tsk3/img/ewf.[ch] not the configure.ac detection of libewf.
libewf version 2 support patch
related trackers: 3367368, 2919095
Update for TSK 3.2.3
https://sourceforge.net/projects/libewf/files/patches%20for%203rd%20party%20software/sleuthkit/
Also know that there is a bug in TSK 3.2.3 ewf.c see the mail.