patch 8.1.0268: file type checking has too many #ifdef

Problem:    File type checking has too many #ifdef.
Solution:   Always define the S_IF macros. (Ken Takata, closes #3306)
diff --git a/src/if_cscope.c b/src/if_cscope.c
index d621a14..186179c 100644
--- a/src/if_cscope.c
+++ b/src/if_cscope.c
@@ -550,7 +550,7 @@
     }
 
     /* if filename is a directory, append the cscope database name to it */
-    if ((statbuf.st_mode & S_IFMT) == S_IFDIR)
+    if (S_ISDIR(statbuf.st_mode))
     {
 	fname2 = (char *)alloc((unsigned)(strlen(CSCOPE_DBFILE) + strlen(fname) + 2));
 	if (fname2 == NULL)
@@ -581,12 +581,7 @@
 
 	i = cs_insert_filelist(fname2, ppath, flags, &statbuf);
     }
-#if defined(UNIX)
     else if (S_ISREG(statbuf.st_mode) || S_ISLNK(statbuf.st_mode))
-#else
-	/* WIN32 - substitute define S_ISREG from os_unix.h */
-    else if (((statbuf.st_mode) & S_IFMT) == S_IFREG)
-#endif
     {
 	i = cs_insert_filelist(fname, ppath, flags, &statbuf);
     }