changes file for bug21242

changes/bug21242

+  o Major bugfixes (entry guards):
+    - Stop trying to build circuits through entry guards for which we
+      have no descriptor yet. Also, stop crashing if we *do* accidentally
+      try to build a circuit in such a state. Fixes bug 21242; bugfix
+      on 0.3.0.1-alpha.
+
+  o Minor features (entry guards):
+    - Do not try to build circuits until we have descriptors for our
+      primary entry guards. Related to fix for bug 21242.
+