Optimize comparisons in `haskell-indentation.el`

This performs the following replacements:

- Replace `equal` with `string=` if at least one operand is a
  string literal.

- Replace `equal` with `eq` if at least one operand is guaranteed to
  be a symbol.

- Replace `member` with `memq` if ELT is a always symbol or if LIST
  contains only symbols.

- Use `match-string-no-properties` instead of `match-string` in
  `haskell-indentation-peek-token` to avoid carrying around unused
  meta-data.