Document hand-coded API functions
Document hand-coded API functions

* librsvg/src/rsvg.hg: Remove redundant "#include <glibmm.h>".
(Rsvg::set_default_dpi): Document both overloads.
(Rsvg::{Dimension,Position}Data): Remove redundant "public".

GNOME/librsvgmm,GNOME/librsvgmm,GNOME/librsvgmm