build: Add cleanup functions

Since it's just using this one header from libgsystem for now, just copy the
header file instead of using a git submodule.
util: Remove unused functions
utils: Use the cleanup attribute to clean up
client: Use the cleanup attribute to clean up
profile: editor: Use the cleanup attribute to clean up
accels: Use the cleanup attribute to clean up
app: Use the cleanup attribute to clean up
utils: Use the cleanup attribute to clean up
widgets: Use the cleanup attribute to clean up
widgets: Use the cleanup attribute to clean up
prefs: Use the cleanup attribute to clean up
profiles: Use the cleanup attribute to clean up
screen: Use the cleanup attribute to clean up
search: Use the cleanup attribute to clean up
profile: Use the cleanup attribute to clean up
window: Use the cleanup attribute to clean up
build: Fix -Wuninitialized warnings

Introduced by cleanup patches.