Merge pull request #20 from colincross/unique

Fix makeUniquePackageNames
diff --git a/context.go b/context.go
index 811ce76..ff3a6ce 100644
--- a/context.go
+++ b/context.go
@@ -1753,6 +1753,7 @@
 			// No collision so far.  Tentatively set the package's name to be
 			// its short name.
 			pkgNames[pctx] = pctx.shortName
+			pkgs[pctx.shortName] = pctx
 		}
 	}