add Formula for pazpar2 1.6.39

pazpar2 is a metasearch software by Index Data.

It seems natural to offer it if the underlying yaz library
and the sibling metaproxy software are available as well.

YMMV but my impression is that ICU support in Homebrew’s current
yaz setup does not work properly (I need an extra
dependency on icu4c for things to work correctly)
which means that ICU support in pazpar2 also does
not work (even though you typically want it).

As icu4c is called problematic, I am hesitant to
add that dependency to yaz myself. If anyone who is
familiar with both yaz and Homebrew wants to discuss
this, please do get in touch.