Removing leading and trailing empty lines from all example files.

Using the following Perl script:
-----------------------------------------------------
#!/usr/bin/perl

local($/) = undef;
my $text = <>;

$text =~ s/\A\n+//mg;
$text =~ s/\n+\Z/\n/mg;

print "$text";
-----------------------------------------------------

Box_intersection_d/examples/Box_intersection_d/minimal.cpp

@@ -18,4 +18,3 @@ int main() {
     CGAL::box_intersection_d( boxes, boxes+9, query, query+2, callback);
     return 0;
 }
-