This make the controller even more lightweight (no extra object, no extra lock,
less indirections). For object that don't use the controller the only 'overhead'
is a 3 unused fields in the gst_object structure.
This changes some APIs in compatible ways:
- Some functions now take "const char *" arguments, not "char *"
- Some structs now have "conts char *" members, not "char *"
The changes may cause warnings when compiling with the right warning
flags. You've been warned.
Also adds -Wwrite-strings as a warning flag in configure.ac.
https://bugzilla.gnome.org/show_bug.cgi?id=611692
