deb pkg: add stuff lost from aggressive refactor

While refactoring package/debian/Makefile.inc from
package/debian/core/Makefile, too much was removed.
add myperl to path in postinst
enable debugging in deb postinst
add more debugging to deb postinst
fix indent in example yaml files for PP Yaml
add perldep mysql
add missing cpanm.mk
travis-ci for debian myperl