patch 8.2.5077: various warnings from clang on MS-Windows

Problem:    Various warnings from clang on MS-Windows.
Solution:   Avoid the warnings. (Yegappan Lakshmanan, closes #10553)
diff --git a/src/dosinst.c b/src/dosinst.c
index 416528c..60e3c64 100644
--- a/src/dosinst.c
+++ b/src/dosinst.c
@@ -1527,7 +1527,7 @@
 		"*\\OpenWithList\\gvim.exe",
 	};
 
-	for (i = 0; ERROR_SUCCESS == lRet && i < ARRAYSIZE(openwith); i++)
+	for (i = 0; ERROR_SUCCESS == lRet && i < (int)ARRAYSIZE(openwith); i++)
 	    lRet = reg_create_key_and_value(hRootKey, openwith[i], NULL, "", flag);
     }