Styles are applied to each node by src/lvrend.cpp setNodeStyle(),
on each rendering and re-rendering, recursively, with the following flow:

1) All nodes default style starts with the constructor values
for css_style_rec_tag() in include/lvstyles.h.
(Some other initial values for the root element style are set in
src/lvtinydom.cpp ldomDocument::setRenderProps())

2) Known elements default styles for display: and white-space: are
then set according to the definitions in include/fb2def.h and the
macros in include/dtddef.h.

3) The "external" stylesheet from this directory and possible style
tweaks declarations are applied to each node if the selector match.

4) Embedded/internal stylesheet are applied in the same way

5) Then, styles inheritance is applied and propagate some styles from
the parent node (what is inherited and how inheritance takes place is
at the end of src/lvrend.cpp setNodeStyle())

