Add poppler-qt5.pc to .gitignore

https://bugs.freedesktop.org/show_bug.cgi?id=79744
Add test-driver to .gitignore

https://bugs.freedesktop.org/show_bug.cgi?id=79744
Add poppler-forms, stress-threads-qt, test-render-to-file to .gitignore

https://bugs.freedesktop.org/show_bug.cgi?id=79744
Add poppler-undeclared.txt to .gitignore

https://bugs.freedesktop.org/show_bug.cgi?id=79744
Add *.gir, *.typelib to glib/.gitignore

https://bugs.freedesktop.org/show_bug.cgi?id=79744
Add Changelog to .gitignore

https://bugs.freedesktop.org/show_bug.cgi?id=79744