Cleanup devhelp codebase with modern glib features
The codebase is pretty old and glib and gobject moved further down the road and introduced new Header macros for cleaner code and introduced g_auto* functions to cleanup resources automatically when the variable goes out of scope. I propose to clean up the code a bit and at least introduce the new header macros. When working on a part of code for refactoring maybe use g_auto* functions for a more modern codebase. I expect this issue is a long runner.