Change the numbering of static ctors/dtors to be module based instead of being global.

This fixes #210 by making sure that the static ctor always gets the same
number, regardless of the order of the modules given at the command line.

dmd/module.h

@@ -179,6 +179,10 @@ struct Module : Package
 
     // array ops emitted in this module already
     StringTable arrayfuncs;
+
+    // for numbering staticCtors etc.
+    int uniqueId;
+    Identifier* generateId(Identifier* id);
 };