stream: Separate TCP/Unix stream helpers from stream/service implementations

This allows us to disable Unix sockets cleanly on Windows. Replaces some
read/write calls with recv/send counterparts, as Winsock does not like
read/writes.

src/libstrongswan/utils/windows.h

@@ -261,6 +261,12 @@ int socketpair(int domain, int type, int protocol, int sv[2]);
  */
 #define EWOULDBLOCK EAGAIN
 
+/**
+ * ECONNRESET is mapped to something arbitrary. It is returned by
+ * stream->read_all() but should not be mapped from a send/recv WSA error.
+ */
+#define ECONNRESET ENXIO
+
 /**
  * recv(2) with support for MSG_DONTWAIT
  */