Tweaking lib/symbols for XML entities

[Pavel Sanda]

On Tue, Jun 09, 2020 at 07:02:23PM +0200, Thibaut Cuvelier wrote:
> This patch is made so that there should not be any change to the XHTML
> output. All features are opt-in (name spaces and XML entities). XHTML
> output always uses HTML entities (which are very lenient), XML ones should
> never be used once this patch is applied.
> 
> That nbsp shouldn't have been modified in the first patch. Here is a new
> version of the set of patches so that the change is only applied in XML
> mode (again, which should not be used right now, because it will only be
> useful for DocBook), with no change in the first one.

Thanks, the patch still doesnot apply to current master.

Another two bits:
1. error check: if you export math manual to html with and without your patch, the output is identical, right?
2. Pleas add comments to those new members (I know the others don't have it either, but that does not make it right :)
+ std::string xmlns_;
+ ///
+ bool xml_mode_;


Pavel