Add libpq's openssl dependencies to pkg-config file
Add libssl and libcrypto to libpq.pc's Requires.private. This allows
static linking to work if those libssl or libcrypto themselves have
dependencies in their *.private fields, such as -lz in some cases.
Reported-by: Sandro Mani <manisandro@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/
837d1dcf-2fca-ee6e-0d7e-
6bce1a1bac75@gmail.com