pgsql: Add pg_nodiscard function declaration specifier

Add pg_nodiscard function declaration specifier

pg_nodiscard means the compiler should warn if the result of a
function call is ignored.  The name "nodiscard" is chosen in alignment
with (possibly future) C and C++ standards.  It maps to the GCC
attribute warn_unused_result.

Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://www.postgresql.org/message-id/flat/e3753562-99cd-b65f-5aca-687dfd1ec2fc@2ndquadrant.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/c617aea6acdd9057a14d91ff294905b1b5509348

Modified Files
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src/include/c.h | 12 ++++++++++++
1 file changed, 12 insertions(+)