drop ghc_compiler and use pkg_name in devel description

ghc-hashable.spec

@@ -6,7 +6,7 @@ Name:           ghc-%{pkg_name}
 # part of haskell-platform-2013.2
 Version:        1.1.2.5
 Release:        3%{?dist}
-Summary:        Class for types convertable to a hash value
+Summary:        Class for types convertible to a hash value
 
 License:        BSD
 URL:            http://hackage.haskell.org/package/%{pkg_name}
@@ -29,13 +29,14 @@ basic types and a way to combine hash values.
 
 %package devel
 Summary:        Haskell %{pkg_name} library development files
-Requires:       %{ghc_compiler}
+Requires:       ghc-compiler = %{ghc_version}
-Requires(post): %{ghc_compiler}
+Requires(post): ghc-compiler = %{ghc_version}
-Requires(postun): %{ghc_compiler}
+Requires(postun): ghc-compiler = %{ghc_version}
 Requires:       %{name} = %{version}-%{release}
 
 %description devel
-This package provides the Haskell hashable library development files.
+This package provides the Haskell %{pkg_name} library development files.
+
 
 %prep
 %setup -q -n %{pkg_name}-%{version}