Merge branch 'ticket27252-033' into ticket27252-034

Semantic merge:
- Rust offline and online were swapped in ticket27252-032

changes/ticket27252

@@ -0,0 +1,6 @@
+  o Minor features (continuous integration):
+    - Skip gcc on OSX in Travis CI, it's rarely used.
+      Skip a duplicate hardening-off build in Travis on Tor 0.2.9.
+      Skip gcc on Linux with default settings, because all the non-default
+      builds use gcc on Linux.
+      Implements ticket 27252.

changes/ticket27252-032

@@ -0,0 +1,5 @@
+  o Minor features (continuous integration):
+    - Only run one online rust build in Travis, to reduce network errors.
+      Skip offline rust builds on Travis for Linux gcc, because they're
+      redundant.
+      Implements ticket 27252.