Use extractbb instead of ebb

ebb was the old tool and looks like it is on its way out, a very least
from Debian and for pdfTeX.

From manpage:
-------------
 Here are more details about the bb and xbb formats:

 The original  ebb  (from dvipdfm) ignored density information in bitmap
 images, and generated bounding boxes with 100px = 72bp = 1in.  Unfortu‐
 nately, screenshots (especially) tend to look bad with this approach.

 So, extractbb (from dvipdfmx) uses density information if present.
 Otherwise, it generates bounding box with 100px = 100bp.  This is what
 pdfTeX does.

Author: cedounet

book/makefile

@@ -97,7 +97,7 @@ ruby_pkg := ../website/Gemfile ../website/Gemfile.lock
 	figures/export_figures.sh $@.pdf
 
 %.xbb: %.jpg
-	ebb -x $<
+	extractbb -x $<
 # }}}
 
 # Pdf {{{