Documentation: some placeholders are lost

Documentation: some placeholders are lost

Some pieces of text in the documentation files use the <...> syntax to
mark named placeholders. However, the conversion done by pandoc from
Markdown to makefile makes some of these placeholders disappear.

The affected elements are those that contain only characters that could
be valid for an e-mail address or a URL, but are not supposed to be one
of both. Also, elements inside `...`-style code blocks are unaffected.

Fix this situation by escaping the < and > characters where the tags
disappear.

Signed-off-by: Gabriel Filion <lelutin@gmail.com>