crypto-api-0.13.3 broken on GHC 7.10.3 and older

[hvr]

It appears that .hs-boot semantics have changed in GHC 8.0 in such a way that you can provide default method implementations referring to module-private entitites, but this wasn't possible in GHC 7.10.3 yet it seems:

Build profile: -w ghc-7.10.3 -O1
In order, the following will be built (use -v for more details):
 - crypto-api-0.13.3 (lib:crypto-api) (first run)
Configuring crypto-api-0.13.3...
Preprocessing library for crypto-api-0.13.3..
Building library for crypto-api-0.13.3..
[ 1 of 11] Compiling Crypto.CPoly     ( Crypto/CPoly.hs, /tmp/crypto-api-0.13.3/dist-newstyle/build/x86_64-linux/ghc-7.10.3/crypto-api-0.13.3/build/Crypto/CPoly.o )
[ 2 of 11] Compiling Crypto.Types     ( Crypto/Types.hs, /tmp/crypto-api-0.13.3/dist-newstyle/build/x86_64-linux/ghc-7.10.3/crypto-api-0.13.3/build/Crypto/Types.o )
[ 3 of 11] Compiling Crypto.Util      ( Crypto/Util.hs, /tmp/crypto-api-0.13.3/dist-newstyle/build/x86_64-linux/ghc-7.10.3/crypto-api-0.13.3/build/Crypto/Util.o )
[ 4 of 11] Compiling Crypto.Random    ( Crypto/Random.hs, /tmp/crypto-api-0.13.3/dist-newstyle/build/x86_64-linux/ghc-7.10.3/crypto-api-0.13.3/build/Crypto/Random.o )
[ 5 of 11] Compiling Crypto.Classes[boot] ( Crypto/Classes.hs-boot, /tmp/crypto-api-0.13.3/dist-newstyle/build/x86_64-linux/ghc-7.10.3/crypto-api-0.13.3/build/Crypto/Classes.o-boot )

Crypto/Classes.hs-boot:32:11: Not in scope: ‘modeEcb'’

Crypto/Classes.hs-boot:35:13: Not in scope: ‘modeUnEcb'’

Crypto/Classes.hs-boot:38:11: Not in scope: ‘modeCbc'’

Crypto/Classes.hs-boot:41:13: Not in scope: ‘modeUnCbc'’

Crypto/Classes.hs-boot:45:11: Not in scope: ‘modeCtr'’

Crypto/Classes.hs-boot:45:20: Not in scope: ‘incIV’

Crypto/Classes.hs-boot:49:13: Not in scope: ‘modeUnCtr'’

Crypto/Classes.hs-boot:49:24: Not in scope: ‘incIV’

Crypto/Classes.hs-boot:53:15: Not in scope: ‘modeCtr’

Crypto/Classes.hs-boot:53:23: Not in scope: ‘incIV’

Crypto/Classes.hs-boot:57:17: Not in scope: ‘modeUnCtr’

Crypto/Classes.hs-boot:57:27: Not in scope: ‘incIV’

Crypto/Classes.hs-boot:61:11: Not in scope: ‘modeCfb'’

Crypto/Classes.hs-boot:64:13: Not in scope: ‘modeUnCfb'’

Crypto/Classes.hs-boot:67:11: Not in scope: ‘modeOfb'’

Crypto/Classes.hs-boot:71:13: Not in scope: ‘modeUnOfb'’

Crypto/Classes.hs-boot:75:15: Not in scope: ‘modeCbc’

Crypto/Classes.hs-boot:79:17: Not in scope: ‘modeUnCbc’

Crypto/Classes.hs-boot:86:15: Not in scope: ‘modeSiv’

Crypto/Classes.hs-boot:93:17: Not in scope: ‘modeUnSiv’

Crypto/Classes.hs-boot:100:11: Not in scope: ‘modeSiv'’

Crypto/Classes.hs-boot:107:13: Not in scope: ‘modeUnSiv'’

Crypto/Classes.hs-boot:111:15: Not in scope: ‘modeEcb’

Crypto/Classes.hs-boot:115:17: Not in scope: ‘modeUnEcb’

Crypto/Classes.hs-boot:120:15: Not in scope: ‘modeCfb’

Crypto/Classes.hs-boot:125:17: Not in scope: ‘modeUnCfb’

Crypto/Classes.hs-boot:129:15: Not in scope: ‘modeOfb’

Crypto/Classes.hs-boot:133:17: Not in scope: ‘modeUnOfb’

As this has started breaking install-plans, I've just added a lower bound on base to prevent the cabal solver from picking up 0.13.3 with GHC 7.10 and older (see https://hackage.haskell.org/package/crypto-api-0.13.3/revisions/).

cc @mightybyte