Improved atk docs for atktext.c
Improved atk docs for atktext.c

Distrotech/atk,collects/atk,zsx/atk,zsx/atk,collects/atk,Distrotech/atk,Distrotech/atk,GNOME/at-spi2-core,GNOME/at-spi2-core,GNOME/at-spi2-core