Add conditional compilation for windows and posix functions.

This adds a Windows-specific versions of several symbols from libcrypto
and openssl(1).

crypto/compat/b_win.c

@@ -0,0 +1,54 @@
+/*
+ * Public domain
+ *
+ * Dongsheng Song <dongsheng.song@gmail.com>
+ * Brent Cook <bcook@openbsd.org>
+ */
+
+#include <ws2tcpip.h>
+
+#include <openssl/bio.h>
+#include <openssl/err.h>
+
+int
+BIO_sock_init(void)
+{
+	/*
+	 * WSAStartup loads the winsock .dll and initializes the networking
+	 * stack on Windows, or simply increases the reference count.
+	 */
+	static struct WSAData wsa_state = {0};
+	WORD version_requested = MAKEWORD(2, 2);
+	static int wsa_init_done = 0;
+	if (!wsa_init_done) {
+		if (WSAStartup(version_requested, &wsa_state) != 0) {
+			int err = WSAGetLastError();
+			SYSerr(SYS_F_WSASTARTUP, err);
+			BIOerr(BIO_F_BIO_SOCK_INIT, BIO_R_WSASTARTUP);
+			return (-1);
+		}
+		wsa_init_done = 1;
+	}
+ 	return (1);
+}
+
+void
+BIO_sock_cleanup(void)
+{
+	/*
+	 * We could call WSACleanup here, but it is easy to get it wrong. Since
+	 * this API provides no way to even tell if it failed, there is no safe
+	 * way to expose that functionality here.
+	 *
+	 * The cost of leaving the networking DLLs loaded may have been large
+	 * during the Windows 3.1/win32s era, but it is small in modern
+	 * contexts, so don't bother.
+	 */
+}
+
+int
+BIO_socket_nbio(int s, int mode)
+{
+	u_long value = mode;
+	return ioctlsocket(s, FIONBIO, &value) != SOCKET_ERROR;
+}