win32: Fix WSAStartup issues

WSAStartup was not being called for pacat and pactl built with meson,
causing them to fail in pa_mainloop_new with "cannot create wakeup
pipe". This issue also affects other applications linking to libpulse
other than the pulseaudio daemon, which calls WSAStartup itself.

When built with autotools, WSAStartup would have been called in
DllMain, which is recommended against by the documentation [1].

To fix these issues, the WSAStartup/WSACleanup calls can be moved
into pa_mainloop_new/pa_mainloop_free.

[1] https://docs.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-wsastartup

Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/456>

src/pulsecore/dllmain.c

@@ -1,53 +0,0 @@
-/***
-  This file is part of PulseAudio.
-
-  Copyright 2006 Pierre Ossman <ossman@cendio.se> for Cendio AB
-
-  PulseAudio is free software; you can redistribute it and/or modify
-  it under the terms of the GNU Lesser General Public License as published
-  by the Free Software Foundation; either version 2.1 of the License,
-  or (at your option) any later version.
-
-  PulseAudio is distributed in the hope that it will be useful, but
-  WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-  General Public License for more details.
-
-  You should have received a copy of the GNU Lesser General Public License
-  along with PulseAudio; if not, see <http://www.gnu.org/licenses/>.
-***/
-
-#ifdef HAVE_CONFIG_H
-#include <config.h>
-#endif
-
-#ifdef OS_IS_WIN32
-
-#include <stdlib.h>
-#include <stdio.h>
-
-#include <windows.h>
-#include <winsock2.h>
-
-extern char *pa_win32_get_toplevel(HANDLE handle);
-
-BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved) {
-    WSADATA data;
-
-    switch (fdwReason) {
-
-    case DLL_PROCESS_ATTACH:
-        if (!pa_win32_get_toplevel(hinstDLL))
-            return FALSE;
-        WSAStartup(MAKEWORD(2, 0), &data);
-        break;
-
-    case DLL_PROCESS_DETACH:
-        WSACleanup();
-        break;
-
-    }
-    return TRUE;
-}
-
-#endif /* OS_IS_WIN32 */