Revert "Remove Diffie-Hellman examples"

This reverts commit bea98b458136029c2585037c74c114ddc5af896e.

Conflicts:
* programs/Makefile:
  * APPS: the layout of the definition has changed. re-add dh_client
    and dh_server appropriately.

Run scripts/generate_visualc_files.pl to account for the added programs.
diff --git a/programs/Makefile b/programs/Makefile
index feec288..6304aee 100644
--- a/programs/Makefile
+++ b/programs/Makefile
@@ -55,7 +55,9 @@
 	aes/crypt_and_hash$(EXEXT) \
 	hash/hello$(EXEXT) \
 	hash/generic_sum$(EXEXT) \
+	pkey/dh_client$(EXEXT) \
 	pkey/dh_genprime$(EXEXT) \
+	pkey/dh_server$(EXEXT) \
 	pkey/ecdh_curve25519$(EXEXT) \
 	pkey/ecdsa$(EXEXT) \
 	pkey/gen_key$(EXEXT) \
@@ -147,10 +149,18 @@
 	echo "  CC    hash/generic_sum.c"
 	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) hash/generic_sum.c $(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
 
+pkey/dh_client$(EXEXT): pkey/dh_client.c $(DEP)
+	echo "  CC    pkey/dh_client.c"
+	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) pkey/dh_client.c   $(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
+
 pkey/dh_genprime$(EXEXT): pkey/dh_genprime.c $(DEP)
 	echo "  CC    pkey/dh_genprime.c"
 	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) pkey/dh_genprime.c $(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
 
+pkey/dh_server$(EXEXT): pkey/dh_server.c $(DEP)
+	echo "  CC    pkey/dh_server.c"
+	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) pkey/dh_server.c   $(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
+
 pkey/ecdh_curve25519$(EXEXT): pkey/ecdh_curve25519.c $(DEP)
 	echo "  CC    pkey/ecdh_curve25519.c"
 	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) pkey/ecdh_curve25519.c   $(LOCAL_LDFLAGS) $(LDFLAGS) -o $@