Updated license_check to work a bit better across line boundries.

Swapped out 'git grep' for 'grep' since it can take in a --max-count flag.
The license _header_ will always be at the top.

Also enabled output so that PR authors can know what the problem files are.

.travis.yml

@@ -302,11 +302,9 @@ matrix:
     - env:
         - NAME=licence_check
       script:
-        - echo 'Checking that there is no GPL licence text in code'
         - |
-          ! git grep -q --ignore-case "gnu general public";
-        - |
-          ! git grep -q --ignore-case "gnu library general public";
+          ! grep --recursive --max-count=100 --ignore-case --exclude .travis.yml \
+          "gnu general\|gnu lesser\|lesser general\|public license"
 
     - env:
         - NAME=include_check