pg_basebackup: Try to fix some failures on Windows.

pg_basebackup: Try to fix some failures on Windows.

Commit ffd53659c46a54a6978bcb8c4424c1e157a2c0f1 messed up the
mechanism that was being used to pass parameters to LogStreamerMain()
on Windows. It worked on Linux because only Windows was using threads.
Repair by moving the additional parameters added by that commit into
the 'logstreamer_param' struct.

Along the way, fix a compiler warning on builds without HAVE_LIBZ.

Discussion: http://postgr.es/m/CA+TgmoY5=AmWOtMj3v+cySP2rR=Bt6EGyF_joAq4CfczMddKtw@mail.gmail.com