Compilation on FreeBSD: endian.h not available, should probably use sys/endian.h

[transplier]

On FreeBSD, #include <endian.h> does not work:

depbase=`echo md5/md5.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`; cc -DHAVE_CONFIG_H -I.      -I /usr/local/include -MT md5/md5.o -MD -MP -MF $depbase.Tpo -c -o md5/md5.o md5/md5.c && mv -f $depbase.Tpo $depbase.Po
md5/md5.c:54:11: fatal error: 'endian.h' file not found
# include <endian.h>
          ^~~~~~~~~~

I believe the correct file to include is sys/endian.h but I'm not 100% on that. Seems to compile like that on my machine but I haven't done much validation.