doc_tree: do not escape input.
doc_tree: do not escape input.

It is the responsibility of the documentation writer to input
valid markdown, including valid html. If existing documentation
contained things like <FOO> (glib had such things), then it
has to be fixed there, escaping prevented the legitimate use
case of inputting valid html.

hotdoc/hotdoc,thiblahute/hotdoc,hotdoc/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc,thiblahute/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc,thiblahute/hotdoc,hotdoc/hotdoc,hotdoc/hotdoc,thiblahute/hotdoc