travis: pre-install re2c for MacOS builds (sequencer)

.travis.yml

@@ -105,3 +105,4 @@ matrix:
   - env: SET=test01
     os: osx
     compiler: clang
+    addons: { homebrew: { packages: ["re2c"], update: true } }

travis/.travis.yml.example-full

@@ -97,6 +97,7 @@ matrix:
   - env: BASE=7.0
     os: osx
     compiler: clang
+    addons: { homebrew: { packages: ["re2c"], update: true } }
 
 # All above jobs can be defined for other branches or releases of EPICS Base
 # by setting BASE to the branch name or release tag name, e.g.