vim-patch:7.4.423

Problem:    expand("$shell") does not work as documented.
Solution:   Do not escape the $ when expanding environment variables.

https://code.google.com/p/vim/source/detail?r=v7-4-423

src/nvim/path.c

@@ -1080,7 +1080,7 @@ gen_expand_wildcards (
           free(p);
           ga_clear_strings(&ga);
           i = mch_expand_wildcards(num_pat, pat, num_file, file,
-              flags);
+              flags | EW_KEEPDOLLAR);
           recursive = FALSE;
           return i;
         }