Improve the generated POD output from PGbasicmacros.pl.

Note:  Don't use comments in POD.  POD is not Perl code.

macros/PGbasicmacros.pl

@@ -2907,13 +2907,18 @@ sub row {
 
 =head2 Macros for displaying images
 
-    Usage:
+Usage:
+
     image($image, width => 100, height => 100, tex_size => 800, alt => 'alt text', extra_html_tags => 'style="border:solid black 1pt"');
-    # where $image can be a local file path or URL
-    # width and height are pixel counts for HTML display, while tex_size is per 1000 applied to linewidth (for example 800 leads to 0.8\linewidth)
+
+where C<$image> can be a local file path or URL, C<width> and C<height> are
+pixel counts for HTML display, while C<tex_size> is per 1000 applied to
+linewidth (for example 800 leads to 0.8\linewidth)
+
     image([$image1,$image2], width => 100, height => 100, tex_size => 800, alt => ['alt text 1','alt text 2'], extra_html_tags => 'style="border:solid black 1pt"');
     image([$image1,$image2], width => 100, height => 100, tex_size => 800, alt => 'common alt text', extra_html_tags => 'style="border:solid black 1pt"');
-    # this produces an array in array context and joins the elements with ' ' in scalar context
+
+this produces an array in array context and joins the elements with C<' '> in scalar context
 
 =cut