tests: Remove shadowed declarations [-Wshadow]

https://bugzilla.gnome.org/show_bug.cgi?id=741261
tests: Fix some build warnings

This removes warnings like:
    ./tests/test-gom-find-specific.c:67:3: warning: initialization discards ‘const’ qualifier from pointer target type

https://bugzilla.gnome.org/show_bug.cgi?id=741261
git: Ignore some generated files

https://bugzilla.gnome.org/show_bug.cgi?id=741261