pgsql: Revert "Remove troublesome Asserts in cost_mergejoin()."

Revert "Remove troublesome Asserts in cost_mergejoin()."

This reverts commit ff68b256a533b398e3420750f34d161aeee4e099.
The recent change to use -fexcess-precision=standard should make those
Asserts safe, and does fix a test case that formerly crashed for me,
so I think there's no need to have a cross-version difference in the
code here.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/2ae2e9c00798685cd75ea0cc5120466bf2027b90

Modified Files
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src/backend/optimizer/path/costsize.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)