We were only able to translate selections and layers (bot not channels
and paths) via the PDB, this new procedure fixes that. Deprecation of
old API and some more transform consistency to follow...
because it confuses gtk-doc and breaks some links. Also change the
"Index of new symbols in GIMP 2.x" sections to be what seems to be the
modern standard (looked at the GLib and GTK+ docs), and update some
other stuff.
Single newlines in procedure descriptions are still considered normal
spaces. But 2 newlines are transformed into 1 newline. 3 newlines into
2 newlines. And so on.
This allows for a start of nicer output in the procedure browser or C
file comments (and consequently in generated html doc).
Works for all item types, and has much less functions and parameters
than the drawable transform API because it uses the new context
states. Untested and not finished!
