Merge branch 'ab/sha1dc-maint'

The "collision detecting" SHA-1 implementation shipped with 2.13
was quite broken on some big-endian platforms and/or platforms that
do not like unaligned fetches.  Update to the upstream code which
has already fixed these issues.

* ab/sha1dc-maint:
sha1dc: update from upstream

diff --cc Makefile
Simple merge