pgsql: Return INT_MAX or INT_MIN from strtoint() on overflow.

Return INT_MAX or INT_MIN from strtoint() on overflow.

Previously, strtoint() set errno to ERANGE on overflow but returned
the result of casting the long value to int. When the value is outside
the range of int, this produces an implementation-defined result that
cannot reliably indicate the direction of overflow. POSIX requires
strtol() to return exactly LONG_MAX or LONG_MIN on overflow, which
permits safe sign-testing or range-testing. By analogy, make
strtoint() return INT_MAX or INT_MIN on overflow.

Back-patch, since future bug fixes may expect this behavior.

Author: Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>
Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Discussion: https://postgr.es/m/A33EE17C-D014-4980-B3DD-AC51588A06EC@gmail.com
Backpatch-through: 14

Branch
------
REL_18_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/ec65cbc00b2ccc82996e1c94b534e1fbf61fbcd1

Modified Files
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src/common/string.c | 8 ++++++++
1 file changed, 8 insertions(+)