[cvs-nhc98] patch applied (hat): Added handling of multiple modules and automatic focus on relevant source part.

[Malcolm Wallace]

Fri Oct  8 04:18:39 PDT 2004  olaf
  * Added handling of multiple modules and automatic focus on relevant source part.
  
  If use occurrence of current redex and siblings (or definition) is not within visible part of source, then part is changed appropriately. This happens every time the current redex is changed by user.
  
  Modules are read on demand. User can change with < and > between modules.
  
  Both change of module and change of redex sibling rotates, going round at end.
  
  A bit of refactoring. Introducing type CursorSeq for handling both modules and redexes.

    M ./src/hattools/HatExplore.hs -90 +220