Best practice for strings across D1 and D2

[nedbrek]

Hello,
   I have some wrappers for C functions which I am exporting to D.

For D1, I can just use char*.

For D2, I get compiler errors when I try to assign string constants to my 
char* variables.  It seems the best way is to make them immutable(char).

1) If I make the functions take immutable(char), will that cause future 
problems when people want to pass in things besides string constants?

2) What is the best way to make the same declarations work for D1 and D2? 
It seems everything inside a "version" statement must parse correctly, and 
D1 doesn't want to parse "immutable(char)"...

Thanks!
Ned