examples/HDBC/MySQL: fix for GHC 7.4.

examples/HDBC/MySQL/hrr-example-HDBC-MySQL.cabal

@@ -12,6 +12,10 @@ build-type:          Simple
 -- extra-source-files:
 cabal-version:       >=1.10
 
+flag ghc74-generic
+  description: Enable for generic programming using old ghc. If true use ghc-prim.
+  default:     False
+
 executable example
   hs-source-dirs:
     src
@@ -24,8 +28,8 @@ executable example
     , MultiParamTypeClasses
     , MonadComprehensions
   build-depends:
-      base >=4.6 && <5
-    , template-haskell >=2.8
+      base >=4.5 && <5
+    , template-haskell >=2.7
     , HDBC >=2.3
     , HDBC-mysql >=0.6 && <0.8
     , HDBC-session
@@ -34,6 +38,9 @@ executable example
     , relational-schemas
     , relational-query-HDBC >= 0.4
     , time
+  if flag(ghc74-generic)
+    build-depends:        ghc-prim == 0.2.*
+
   default-language:
     Haskell2010
   ghc-options: