MacOS installer: Uninstaller must be able to deal with ATiger receipts

distrib/MacOS/installer-scripts/Uninstaller

@@ -68,6 +68,8 @@ echo "Removing ${INSTALL_DEST}/GHC.framework"
 rm -rf ${INSTALL_DEST}/GHC.framework
 
 echo "Removing package recipt"
+# The first is for Leopard packages and the second for Tiger packages.
 rm -f /Library/Receipts/boms/org.haskell.glasgowHaskellCompiler.ghc.pkg.bom
+rm -rf /Library/Receipts/ghc.pkg
 
 echo "${INSTALL_DEST}/GHC.framework has been purged!"