[Groff] new grohtml bug

[Werner LEMBERG]

Consider the following snippet (to be processed with `-Thtml') -- the
code is useless; it just shows the bug:

  .tag "html-tag:.NH 1
  (\c
  .tag "html:xxx)

The expected output is

  <a name="(xxx)"></a>
  <h2>(xxx)</h2>

or this

  (<a name="xxx)"></a>
  <h2>(xxx)</h2>

-- I'm not sure.

Instead, we get the following

  <a name="( xxx)"></a>
  <h2>( xxx)</h2>

which is definitely wrong.  Conclusion: If the `.NH' grohtml tag is
active, the `\c' escape is handled incorrectly.

BTW, a real-world example is this (to be processed with -mwww):

  .HnS 1
  GNU Troff (\c
  .URL http://\:groff.ffii.org/ Groff )
  \[em] a
  .URL http://\:www.gnu.org/ GNU
  project.
  .HnE


    Werner