Remove SHA256 EVP wrapper implementation.

All supported versions of OpenSSL should now have SHA256 so remove our
EVP wrapper implementaion.  ok djm@
diff --git a/Makefile.in b/Makefile.in
index 5870e9e..e247c0d 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -80,7 +80,7 @@
 	canohost.o channels.o cipher.o cipher-aes.o cipher-aesctr.o \
 	cipher-bf1.o cipher-ctr.o cipher-3des1.o cleanup.o \
 	compat.o crc32.o deattack.o fatal.o hostfile.o \
-	log.o match.o md-sha256.o moduli.o nchan.o packet.o opacket.o \
+	log.o match.o moduli.o nchan.o packet.o opacket.o \
 	readpass.o rsa.o ttymodes.o xmalloc.o addrmatch.o \
 	atomicio.o key.o dispatch.o mac.o uidswap.o uuencode.o misc.o utf8.o \
 	monitor_fdpass.o rijndael.o ssh-dss.o ssh-ecdsa.o ssh-rsa.o dh.o \