pgsql: Guard against overflow in make_interval().

Guard against overflow in make_interval().

The original code did very little to guard against integer or floating
point overflow when computing the interval's fields.  Detect any such
overflows and error out, rather than silently returning bogus results.

Joseph Koshakow, reviewed by Ashutosh Bapat and me.

Discussion: https://postgr.es/m/CAAvxfHcm1TPwH_zaGWuFoL8pZBestbRZTU6Z%3D-RvAdSXTPbKfg%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b2d55447a563036579d6777f64a7483dceeab6ea

Modified Files
--------------
src/backend/utils/adt/timestamp.c      | 39 ++++++++++++++++++++++++----------
src/include/datatype/timestamp.h       |  1 +
src/test/regress/expected/interval.out | 27 +++++++++++++++++++++++
src/test/regress/sql/interval.sql      | 15 +++++++++++++
4 files changed, 71 insertions(+), 11 deletions(-)