[cvs-nhc98] patch applied (hat): Use unsafePerform in a safer way, so that marshalling of strings and arrays also works with nhc98.

[Malcolm Wallace]

Tue Apr 30 09:46:51 PDT 2002  olaf
  * Use unsafePerform in a safer way, so that marshalling of strings and arrays also works with nhc98.
  
  Also modified constUse to ensure that black hole errors are correctly located in the trace. However, the constUse is already evaluated when the black hole error occurs. So using a stack for entering/result would probably lead to wrong error position.

    M ./src/hatlib/Hat.hs -27 +37