patch applied (cabal): Add some diagnostic info to some internal errors

[Ian Lynagh]

Sat May 15 12:38:10 PDT 2010  Ian Lynagh <igloo at earth.li>
  * Add some diagnostic info to some internal errors
  When giving an "internal error: unexpected package db stack" error, say
  what the stack is.

    M ./Distribution/Simple/GHC.hs -1 +1
    M ./Distribution/Simple/LHC.hs -1 +1
    M ./Distribution/Simple/Program/HcPkg.hs -1 +1

View patch online:
http://darcs.haskell.org/cgi-bin/darcsweb.cgi?r=cabal;a=darcs_commitdiff;h=20100515193810-3fd76-9267a6def08ee3abc56ec56c191cc55e7204c81a.gz