pgsql: Fix mistakes in commit d45099425eb19e420433c9d81d354fe585f4dbd6.

Fix mistakes in commit d45099425eb19e420433c9d81d354fe585f4dbd6.

I intended to include a change to the "skip" count in the test
case, but it didn't get folded into the commit. Do that now,
so that non-zlib builds don't break.

The new file bbstreamer_gzip.c needs <unistd.h> to avoid
complaints about dup() not having a prototype, as per buildfarm
returns.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/da505eafca81bc81c34f729521a42a093408cb92

Modified Files
--------------
src/bin/pg_basebackup/bbstreamer_gzip.c  | 2 ++
src/bin/pg_verifybackup/t/009_extract.pl | 2 +-
2 files changed, 3 insertions(+), 1 deletion(-)