specify version bounds in pgf.cabal and pgf2.cabal

src/runtime/haskell-bind/pgf2.cabal

@@ -23,9 +23,9 @@ library
     PGF2.Expr,
     PGF2.Type
   build-depends:
-    base >=4.3 && <5,
-    containers,
-    pretty
+    base >= 4.9.1 && <4.15,
+    containers >= 0.5.7 && < 0.7,
+    pretty >= 1.1.3 && < 1.2
   default-language: Haskell2010
   build-tools: hsc2hs
   extra-libraries: pgf gu

src/runtime/haskell/pgf.cabal

@@ -14,16 +14,16 @@ tested-with: GHC==7.6.3, GHC==7.8.3, GHC==7.10.3, GHC==8.0.2, GHC==8.4.4
 library
   default-language: Haskell2010
   build-depends:
-    array,
-    base >= 4.6 && <5,
-    bytestring,
-    containers,
+    base >= 4.9.1 && <4.15,
+    array >= 0.5.1 && < 0.6,
+    containers >= 0.5.7 && < 0.7,
+    bytestring >= 0.10.8 && < 0.11,
+    utf8-string >= 1.0.1.1 && < 1.1,
+    random >= 1.1 && < 1.3,
+    pretty >= 1.1.3 && < 1.2,
+    mtl >= 2.2.1 && < 2.3,
+    ghc-prim >= 0.5.0 && < 0.7
     -- exceptions,
-    ghc-prim,
-    mtl,
-    pretty,
-    random,
-    utf8-string
 
   other-modules:
     -- not really part of GF but I have changed the original binary library