gcrypt: define libssh2_sha256_ctx
Looks like it didn't make it into the latest commit for whatever reason.
Closes #58
diff --git a/src/libgcrypt.h b/src/libgcrypt.h
index 931a7a4..20062ed 100644
--- a/src/libgcrypt.h
+++ b/src/libgcrypt.h
@@ -74,6 +74,8 @@
#define libssh2_sha1(message, len, out) \
gcry_md_hash_buffer (GCRY_MD_SHA1, out, message, len)
+#define libssh2_sha256_ctx gcry_md_hd_t
+
#define libssh2_sha256_init(ctx) \
(GPG_ERR_NO_ERROR == gcry_md_open (ctx, GCRY_MD_SHA256, 0))
#define libssh2_sha256_update(ctx, data, len) \
