sws: fix binding to unix socket on Windows

Windows 10.17063+ (having unix socket support) fails to set for unix
sockets the `SO_REUSEADDR` option, with error 10045 (`WSAEOPNOTSUPP`),
and also fails to set `SO_KEEPALIVE` with error 10042 (`WSAENOPROTOOPT`).

Fix by not enabling these socket options on Windows for unix sockets.

Also:
- fixing test 1435, 1436 to run in CI.
- fixing the `socksd` test server for test 1467, 1468, 1470. But, also
  disable these for now due to another Windows issue: #19825

Ref: https://stackoverflow.com/questions/68791319/unix-domain-socket-bind-failed-in-windows/68794755#68794755
Ref: #19810
Closes #19812

tests/data/test1467

@@ -30,9 +30,11 @@ Funny-head: yesyes
 #
 # Client-side
 <client>
+# --socks5 cannot accept Windows absolute paths
 <features>
 proxy
 UnixSockets
+!win32
 </features>
 <server>
 http

tests/data/test1468

@@ -31,9 +31,11 @@ Funny-head: yesyes
 #
 # Client-side
 <client>
+# --socks5h cannot accept Windows absolute paths
 <features>
 proxy
 UnixSockets
+!win32
 </features>
 <server>
 http

tests/data/test1470

@@ -32,9 +32,11 @@ Funny-head: yesyes
 #
 # Client-side
 <client>
+# --proxy cannot accept Windows absolute paths
 <features>
 proxy
 UnixSockets
+!win32
 </features>
 <server>
 https