patch 7.4.1334
Problem:    Many compiler warnings with MingW.
Solution:   Add type casts. (Yasuhiro Matsumoto)
diff --git a/src/main.c b/src/main.c
index e412641..fac4be1 100644
--- a/src/main.c
+++ b/src/main.c
@@ -3940,7 +3940,7 @@
     }
     cdp = vim_strsave_escaped_ext(cwd,
 #ifdef BACKSLASH_IN_FILENAME
-		    "",  /* rem_backslash() will tell what chars to escape */
+		    (char_u *)"",  /* rem_backslash() will tell what chars to escape */
 #else
 		    PATH_ESC_CHARS,
 #endif