Improve clutter_text_get_chars doc
Improve clutter_text_get_chars doc

Explicitly explain that end_pos is not included with the resulting
string

http://bugzilla.clutter-project.org/show_bug.cgi?id=2081

rkudiyarov/clutter_osx,ebassi/clutter,djdeath/clutter-multithreaded,djdeath/clutter-android,GNOME/clutter,jigpu/clutter,djdeath/clutter,rkudiyarov/clutter_osx,rkudiyarov/clutter_osx,collects/clutter,djdeath/clutter-multithreaded,ebassi/clutter,Distrotech/clutter,djdeath/clutter,jigpu/clutter,collects/clutter,nobled/clutter,GNOME/clutter,spatulasnout/clutter,spatulasnout/clutter,djdeath/clutter-android,dlespiau/clutter,Distrotech/clutter,jigpu/clutter,spatulasnout/clutter,collects/clutter,heysion/clutter-clone,ebassi/clutter,GNOME/clutter,heysion/clutter-clone,djdeath/clutter,spatulasnout/clutter,ebassi/clutter,Distrotech/clutter,nobled/clutter,dlespiau/clutter,jigpu/clutter,djdeath/clutter,Distrotech/clutter,kerrickstaley/clutter-vala,djdeath/clutter-multithreaded,nobled/clutter,collects/clutter,djdeath/clutter,djdeath/clutter-android,djdeath/clutter-android,kerrickstaley/clutter-vala,collects/clutter,GNOME/clutter,Distrotech/clutter,GNOME/clutter,heysion/clutter-clone,djdeath/clutter-multithreaded,heysion/clutter-clone,ebassi/clutter,dlespiau/clutter,djdeath/clutter-android,kerrickstaley/clutter-vala,Distrotech/clutter,rkudiyarov/clutter_osx,heysion/clutter-clone,spatulasnout/clutter,jigpu/clutter,djdeath/clutter,jigpu/clutter,kerrickstaley/clutter-vala