Components of a package name should not begin with a digit

Avoids ambiguities with package identifiers like "foo-1" (the 1 is the
version number). 

Distribution/Package.hs

@@ -46,7 +46,7 @@ module Distribution.Package (
 
 import Distribution.Version
 import Distribution.Compat.ReadP as ReadP
-import Data.Char ( isAlphaNum )
+import Data.Char ( isAlpha, isAlphaNum )
 import Data.List ( intersperse )
 
 data PackageIdentifier
@@ -62,8 +62,14 @@ showPackageId pkgid =
   pkgName pkgid ++ '-': showVersion (pkgVersion pkgid)
 
 parsePackageName :: ReadP r String
-parsePackageName = do ns <- sepBy1 (munch1 isAlphaNum) (char '-')
+parsePackageName = do ns <- sepBy1 component (char '-')
                       return (concat (intersperse "-" ns))
+  where component = do 
+	   c <- satisfy isAlpha
+	   cs <- munch isAlphaNum
+	   return (c:cs)
+	-- each component begins with an alphabetic character, to avoid
+	-- ambiguity in identifiers like foo-1 (the 1 is the version number).
 
 parsePackageId :: ReadP r PackageIdentifier
 parsePackageId = do