patch applied (ghc): FIX BUILD addDLL returns const char*

[Simon Marlow]

Thu Sep 27 06:26:19 PDT 2007  jochemberndsen at dse.nl
  * FIX BUILD addDLL returns const char*
  addDLL returns const char*, not just a char*.
  Fix compiler warning

    M ./includes/Linker.h -1 +1
    M ./rts/Linker.c -2 +2