patch 9.0.1023: MS-Windows: dynamic loading of libsodium doesn't work

Problem:    MS-Windows: dynamic loading of libsodium doesn't work.
Solution:   Add "randombytes_random". (Ken Takata, closes #11667)
diff --git a/src/proto/crypt.pro b/src/proto/crypt.pro
index 7913694..560e30b 100644
--- a/src/proto/crypt.pro
+++ b/src/proto/crypt.pro
@@ -26,4 +26,6 @@
 void crypt_append_msg(buf_T *buf);
 int crypt_sodium_munlock(void *const addr, const size_t len);
 void crypt_sodium_randombytes_buf(void *const buf, const size_t size);
+int crypt_sodium_init(void);
+uint32_t crypt_sodium_randombytes_random(void);
 /* vim: set ft=c : */