[perl #60970] xsubpp "-s pattern" not documented in manual page

I just pushed a documentation patch to ExtUtils::ParseXS for this 
(including a weak discouragement from using that obscure option).

The change is in the EU::ParseXS github repository because there is a 
number of changes there pending a CPAN smoke or more desperate action. 
Once that's resolved, I'll port this change to core along with the others 
that have accumulated.

• [perl #60970] xsubpp "-s pattern" not documented in manual page by Steffen Mueller via RT