Revert "Suppress Octave failing the build"

- This reverts commit fea2fc137e.
- Failures were probably due to gcc running out of memory
- Disabling optimization of Octave tests should both increase
  compile times and reduce memory usage, and reducing number
  of make jobs to 3 should also allow for more memory per job

.travis.yml

@@ -51,9 +51,7 @@ matrix:
     - compiler: gcc
       env: SWIGLANG=tcl
   allow_failures:
-    # g++-4.6.3 internal compiler error for li_std_vector testcase
-    - compiler: gcc
-      env: SWIGLANG=octave SWIGJOBS=-j4
+    # None
 before_install:
   - date -u
   - uname -a