* normaliseFState() now locks all output paths prior to building, thus

ensuring that simultaneous invocations of Nix don't clobber
  each other's  builds.

* Fixed a bug in `make install'.

src/pathlocks.hh

@@ -0,0 +1,18 @@
+#ifndef __PATHLOCKS_H
+#define __PATHLOCKS_H
+
+#include "util.hh"
+
+
+class PathLocks 
+{
+private:
+    list<int> fds;
+
+public:
+    PathLocks(const Strings & _paths);
+    ~PathLocks();
+};
+
+
+#endif /* !__PATHLOCKS_H */