[doc] < is not always escaped in HTML generation

[fperrad]

in PIR block (=begin/end), the character < is not escaped to a valid HTML entity.

for example in book/ch03_pir.pod :

<pre>  .sub _main
      $I0 = 42
      $I1 = 43
      if $I0 < $I1 goto L1
      print "never printed"
  L1:
      print "after branch\n"
      end
  .end
</pre>

[allison]

Which Pod parser?

[fperrad]

I simply run 'make html'

So, I use the Parrot stuff in lib/Parrot/Docs and a Strawberry Perl 5.10.0 which comes with

Pod::Simple 3.05

[coke]

See also #559