Build fails with OpenSSL 1.1

Debian sid has openssl 1.1.0c:

[ 10/103] Compiling libntp/a_md5encrypt.c
../../libntp/a_md5encrypt.c: In function ‘MD5authencrypt’:
../../libntp/a_md5encrypt.c:55:13: error: storage size of ‘ctx’ isn’t known
  EVP_MD_CTX ctx;
             ^~~
../../libntp/a_md5encrypt.c:55:13: warning: unused variable ‘ctx’ [-Wunused-variable]
../../libntp/a_md5encrypt.c: In function ‘MD5authdecrypt’:
../../libntp/a_md5encrypt.c:93:13: error: storage size of ‘ctx’ isn’t known
  EVP_MD_CTX ctx;
             ^~~
../../libntp/a_md5encrypt.c:93:13: warning: unused variable ‘ctx’ [-Wunused-variable]
../../libntp/a_md5encrypt.c: In function ‘addr2refid’:
../../libntp/a_md5encrypt.c:129:13: error: storage size of ‘ctx’ isn’t known
  EVP_MD_CTX ctx;
             ^~~
../../libntp/a_md5encrypt.c:129:13: warning: unused variable ‘ctx’ [-Wunused-variable]

Waf: Leaving directory `/home/selsky/ntpsec/build/main'
Build failed
 -> task in 'ntp' failed with exit status 1 (run with -v to display more information)

swalker posted a patch from Classic on IRC: http://pastebin.com/raw/wnJs5QLL backported from classic http://bugs.ntp.org/show_bug.cgi?id=3095