Initialize libgcrypt.

We relied initialization of libgcrypt on gnutls_global_init(), but
recent change in gnutls, which changes default crypto backend from
libgcrypt to libnettle, leaves libgcrypt uninitialized if it uses
libnettle as backend(and this is likely because libnettle is chosen by
default). To fix this issue, we simply initialize libgcrypt on our
own.

src/Platform.cc

@@ -58,6 +58,9 @@
 # include <openssl/err.h>
 # include <openssl/ssl.h>
 #endif // HAVE_OPENSSL
+#ifdef HAVE_LIBGCRYPT
+# include <gcrypt.h>
+#endif // HAVE_LIBGCRYPT
 #ifdef HAVE_LIBGNUTLS
 # include <gnutls/gnutls.h>
 #endif // HAVE_LIBGNUTLS
@@ -103,6 +106,13 @@ bool Platform::setUp()
   SSL_load_error_strings();
   SSL_library_init();
 #endif // HAVE_OPENSSL
+#ifdef HAVE_LIBGCRYPT
+  if(!gcry_check_version(GCRYPT_VERSION)) {
+    throw DL_ABORT_EX("gcry_check_version() failed.");
+  }
+  gcry_control(GCRYCTL_DISABLE_SECMEM, 0);
+  gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0);
+#endif // HAVE_LIBGCRYPT
 #ifdef HAVE_LIBGNUTLS
   {
     int r = gnutls_global_init();