Add PostgreSQL build feature Perl

[AndreMikulec]

Consider
https://github.com/msys2/MINGW-packages/blame/master/mingw-w64-postgresql/postgresql-9.5.1-pl-perl.patch

Consider
Strawberry Perl (that I a may have used in the past)

See my old notes.

NOTE: I would have to very late (inside PKGBUILD) add Perl information

Consider
https://github.com/archlinux/svntogit-packages/blob/packages/postgresql/trunk/PKGBUILD
https://github.com/archlinux/svntogit-packages/tree/packages/postgresql/trunk
https://archlinux.org/packages/extra/x86_64/postgresql/

Consider
https://github.com/archlinux/svntogit-packages/blob/packages/postgresql/trunk/PKGBUILD
https://github.com/archlinux/svntogit-packages/tree/packages/postgresql/trunk
https://archlinux.org/packages/extra/x86_64/postgresql-libs/

Consider
https://github.com/archlinux/svntogit-packages/blob/packages/postgresql-old-upgrade/trunk/PKGBUILD
https://github.com/archlinux/svntogit-packages/tree/packages/postgresql-old-upgrade/trunk
https://archlinux.org/packages/extra/x86_64/postgresql-old-upgrade/