libsearpc: Update to "new" version, switch to git download method

Upstream changed the v3.2.0 tag. Previously it referred to
haiwen/libsearpc@23f581b39f; now it refers
to haiwen/libsearpc@d1fd7518a2.

This changes the packaged version to the "new" v3.2.0 and switches to
using the git download method (technically the github_archive method),
since the codeload filenames of the previous and current versions are
the same but the files have different hashes.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

libs/libsearpc/patches/001-fix-memory-leak-GH-48.patch

@@ -1,19 +0,0 @@
-From 9b2e2dc65213fb22ed400dc54e4c2279564df62b Mon Sep 17 00:00:00 2001
-From: ly1217 <yu.liu@seafile.com>
-Date: Thu, 31 Oct 2019 00:31:38 -0700
-Subject: [PATCH] Fix memory leak.
-
----
- lib/searpc-named-pipe-transport.c | 1 +
- 1 file changed, 1 insertion(+)
-
---- a/lib/searpc-named-pipe-transport.c
-+++ b/lib/searpc-named-pipe-transport.c
-@@ -377,6 +377,7 @@ void searpc_free_client_with_pipe_transp
-     close(pipe_client->pipe_fd);
- #endif
-     g_free (pipe_client);
-+    g_free (data->service);
-     g_free (data);
-     searpc_client_free (client);
- }