Not quite working in terminal vim

I know this has many gotchas, but I found that to use alt mappings in terminal vim, I have to use `\e` instead of `\<Esc>`

``` diff
-exe "set <M-".a:char.">=\<Esc>".a:char
+exe "set <M-".a:char.">=\e".a:char
```

I dunno why though O.o
