>> It should come with binutils. Google shows a lot of bug reports 
for
>> several distros saying that this file should be installed.
>
>thanks for that info.  I copied in demangle.h from Slackware's
>binutils source package and all seems to be good.  (tdebase 
>compiled successfully, anyway.)

This is not a palatable solution. As mentioned, searching the web 
reveals that including demangle.h in binutils is not something that 
can be presumed. Although some distros have been patched, not all 
have been patched. Trinity has to build against stock distros and 
not kludges.

I've emailed the Slackware maintainer but there is no guarantee a 
patched binutils is forthcoming.

Can the original commit be rewritten to not use demangle.h? 
Otherwise the only solution is reversing the original commit. I 
believe that code was committed primarily as a troubleshooting aid 
against bug report 1288. Therefore reversing the patch should not 
cause any problems, but do we want to keep that code in GIT 
permanently, even after bug report 1288 is resolved?

Darrell