manager: call gnutls_global_init/deinit on Windows

We use the ShiftMediaProject repo for gnutls and it seems the
initialization is still required on Windows. This commit prevents
the client from having to do it.

Change-Id: Id358a61fe6d0f2809d840a18978567dc309963d8

src/manager.cpp

@@ -758,6 +758,10 @@ Manager::init(const std::string& config_file)
         JAMI_ERR("Unable to initialize git transport %s", error ? error->message : "(unknown)");
     }
 
+#if defined _MSC_VER
+    gnutls_global_init();
+#endif
+
 #ifndef WIN32
     // Set the max number of open files.
     struct rlimit nofiles;
@@ -918,6 +922,10 @@ Manager::finish() noexcept
         if (pimpl_->ioContextRunner_.joinable())
             pimpl_->ioContextRunner_.join();
 
+#if defined _MSC_VER
+        gnutls_global_deinit();
+#endif
+
     } catch (const VoipLinkException& err) {
         JAMI_ERR("%s", err.what());
     }