Provide gettid and gethostbyname_r.
Fix build with opaque HMAC_CTX in LibreSSL 3.5.

Index: libdroplet/src/utils.c
--- libdroplet/src/utils.c.orig
+++ libdroplet/src/utils.c
@@ -72,6 +72,13 @@ gettid()
 {
   return syscall(SYS_gettid);
 }
+#elif defined(__OpenBSD__)
+#include <unistd.h>
+pid_t
+gettid(void)
+{
+  return getpid();
+}
 
 #else
 #include <syscall.h>
@@ -120,6 +127,17 @@ linux_gethostbyname_r(const char *name,
   *result = resultp;
 
   return 0;
+#elif defined(__OpenBSD__)
+
+  struct hostent *resultp;
+
+  resultp = gethostbyname(name);
+  if (NULL == resultp)
+    return 1;
+
+  *result = resultp;
+
+  return 0;
 #else
   //linux
   return gethostbyname_r(name, ret, buf, buflen, result, h_errnop);
@@ -475,14 +493,14 @@ dpl_hmac_sha1(const char *key_buf,
               unsigned int data_len,
               char *digest_buf)
 {
-  HMAC_CTX ctx;
+  HMAC_CTX *ctx;
   u_int digest_len;
 
-  HMAC_CTX_init(&ctx);
-  HMAC_Init_ex(&ctx, key_buf, key_len, EVP_sha1(), NULL);
-  HMAC_Update(&ctx, (u_char *) data_buf, data_len);
-  HMAC_Final(&ctx, (u_char *) digest_buf, &digest_len);
-  HMAC_CTX_cleanup(&ctx);
+  ctx = HMAC_CTX_new();
+  HMAC_Init_ex(ctx, key_buf, key_len, EVP_sha1(), NULL);
+  HMAC_Update(ctx, (u_char *) data_buf, data_len);
+  HMAC_Final(ctx, (u_char *) digest_buf, &digest_len);
+  HMAC_CTX_free(ctx);
 
   return digest_len;
 }