pgsql: Use IEEE infinity, not 1e10, for null-and-not-null case in gistp

Use IEEE infinity, not 1e10, for null-and-not-null case in gistpenalty().

Use of a randomly chosen large value was never exactly graceful, and
now that there are penalty functions that are intentionally using infinity,
it doesn't seem like a good idea for null-vs-not-null to be using something
less.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/9f4563f743eab0682f908d51fa3a9c630b31322d

Modified Files
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src/backend/access/gist/gistutil.c |    7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)