Use threaded runtime when linking Haskell unit tests
Use threaded runtime when linking Haskell unit tests

...but only for GHC>7.6.x due to a bug in the base library.

Using the threaded runtime allows us to run the unit tests in parallel.
Set the default runtime options to use as many CPUs as available.

While here, remove the unused HEXTRA_INT Make variable.

Signed-off-by: Brian Foley <a00e555871a6a538e97f8c44307104c884f8e869@google.com>
Reviewed-by: Viktor Bachraty <a13ea37fcfcda126dc54f94389ded93f402eee93@google.com>

mbakke/ganeti,leshchevds/ganeti,onponomarev/ganeti,andir/ganeti,ganeti/ganeti,andir/ganeti,mbakke/ganeti,yiannist/ganeti,leshchevds/ganeti,yiannist/ganeti,onponomarev/ganeti,ganeti/ganeti,yiannist/ganeti,ganeti/ganeti,leshchevds/ganeti,andir/ganeti,mbakke/ganeti