patch 8.1.0604: autocommand test fails on MS-Windows

Problem:    Autocommand test fails on MS-Windows.
Solution:   Use pathcmp() instead of strcmp() to check if a directory differs.
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index e700f2e..466e77e 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -9185,7 +9185,7 @@
 	}
 #endif
 	dir_differs = new_dir == NULL || prev_dir == NULL
-					     || STRCMP(prev_dir, new_dir) != 0;
+			|| pathcmp((char *)prev_dir, (char *)new_dir, -1) != 0;
 	if (new_dir == NULL || (dir_differs && vim_chdir(new_dir)))
 	    EMSG(_(e_failed));
 	else