codegen: Support deprecating properties and their accessors

Use G_PARAM_DEPRECATED for properties and in addition their accessor
methods will be marked as deprecated.

Guard internal accessors calls with G_GNUC_BEGIN/END_IGNORED_DEPRECATIONS
to silence unavoidable warnings.

Based on patch by Simon Werbeck <simon.werbeck@gmail.com>

https://bugzilla.gnome.org/show_bug.cgi?id=732449