mirrors.nix: add http://backpan.perl.org/ for old CPAN modules

It seems only the latest version of perl modules are in CPAN(?). The
BackPan claims to have a complete history of CPAN.
Update isync to 1.0.6
haskell-DAV: update to version 0.4
haskell-basic-prelude: update to version 0.3.5.0
haskell-certificate: update to version 1.3.7
haskell-conduit: update to version 1.0.5
haskell-crypto-pubkey-types: update to version 0.3.2
haskell-crypto-pubkey: update to version 0.1.3
haskell-cryptocipher: update to version 0.5.0
haskell-ghc-vis: update to version 0.7.0.1
haskell-pool-conduit: update to version 0.1.2
haskell-reflection: update to version 1.3
haskell-skein: update to version 1.0.3
haskell-uuid: update to version 1.2.12
haskell-yaml: update to version 0.8.2.4
haskell-hledger-interest: update to version 1.4.3
haskell-DAV: update to version 0.4.1
haskell-asn1-types: update to version 0.1.3
haskell-binary: update to version 0.7.1.0
haskell-hledger-lib: update to version 0.20