public std.traits.isDesiredUDA

[Jonathan Levi]

Would it be reasonable for the private template `isDesiredUDA` 
from std.traits to be made public?

I have twice now copied it (with attribution) into the source 
file of mine.

It can be used to test a single symbol.
Or in my latest case, to test an AliasSeq of UDAs from multiple 
sources (one source of which is not actually from UDAs but from 
template arguments).