Tweak hlblx implementation

Tweak hlblx implementation

Move the patch point from prior to name:delim to after, using the
upstream name:hook macros.  This avoids applying formatting to
delimiters (and so avoids the need to patch name:delim) and so eases
more expressive fomatting, including coloration, e.g.:

\makeatletter
\renewcommand*{\hlblx@format}{\color{blue}}
\makeatother