Test `b2 -n status` from a release layout

.travis.yml

@@ -50,6 +50,9 @@ matrix:
     # Simple integrated status tests check.
     - env: SCRIPT=ci_boost_status
 
+    # Same, but using release layout
+    - env: SCRIPT=ci_boost_status RELEASE=1
+
     # Run 'quick' tests.
     - env: SCRIPT=ci_boost_status TARGET=quick TOOLSET=gcc CXXSTD=03,11
       compiler: g++