[LyX/master] Need this for std::endl now, according to Eugene

[Richard Kimberly Heck]

commit da362a6a59a7d2bd2bb922a0daa782202f9623e2
Author: Richard Kimberly Heck <rikiheck at lyx.org>
Date:   Sat Jun 6 13:05:43 2020 -0400

    Need this for std::endl now, according to Eugene
---
 src/support/os_win32.cpp |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/src/support/os_win32.cpp b/src/support/os_win32.cpp
index 82e57d2..e4f9ebd 100644
--- a/src/support/os_win32.cpp
+++ b/src/support/os_win32.cpp
@@ -32,6 +32,7 @@
 #include "support/lassert.h"
 
 #include <cstdlib>
+#include <iostream>
 #include <vector>
 
 #include <QString>