echo statements with PATH list variables gain spaces

[kevingriffin]

Found while testing NixOS/nixpkgs#108947

When echo statements of PATH variables are converted, they don't come back in tact: fish will echo a PATH with colons in it with spaces instead. If this value is saved somewhere, the colons will become spaces, which wouldn't occur in the original bash.

[bouk]

Solution: #10

I probably need to quote everything all the time, because if a variable is an array you'll get unexpected results (i.e. cartesian products)