pfff/demo: show all names of functions and classes

Summary:
I added two files that try to extract function and class
definations, and print them out

Test Plan:
test on demos/*.php and manually check if anything is
missing.

Reviewers: pad

Differential Revision: https://phabricator.fb.com/D841335
Merge branch 'master' of git://github.com/facebook/pfff
Merge branch 'master' of git://github.com/facebook/pfff
Merge branch 'master' of git://github.com/facebook/pfff
Merge branch 'master' of github.com:facebook/pfff