Enable P6_DOC_TEST_VERSBOSE during make test

To make travis tell us more about what it's not happy about
with recent failures.

Author: zoffixznet

.travis.yml

@@ -47,7 +47,7 @@ install:
   - travis_retry zef --/tap-harness --depsonly install .
 
 script:
-  - make test
+  - P6_DOC_TEST_VERSBOSE=1 make test
   - export CXX=$(command -v g++-4.8 >/dev/null 2>&1; if [ $? -eq 1 ]; then printf "g++"; else printf "g++-4.8"; fi)
   - $CXX --version
   - make html-nohighlight