Bug#1012569: haskell_devscripts: unable to parse CABAL_VERSION from some .cabal files

[Scott Talbert]

Package: haskell-devscripts
Severity: important

haskell-devscripts is unable to parse the CABAL_VERSION out of some
.cabal files.  This is only recently a problem because prior to the
recent perl changes, builds would not fail if CABAL_VERSION was empty.
An example of a package where the .cabal file cannot be parsed is
haskell-base-prelude.  This results in an error such as this:

> dh_haskell_install_haddock --package=libghc-base-prelude-doc --source-dir="debian/tmp-inst-ghc"
> Need CABAL_VERSION to install HTML documentation. at /usr/bin/dh_haskell_install_haddock line 46.
> make: *** [/usr/share/cdbs/1/class/hlibrary.mk:188: install/libghc-base-prelude-doc] Error 25

haskell-devscripts should be updated to perform parsing of the .cabal
file more reliably.