pgsql: Define pg_attribute_cold and pg_attribute_hot macros

Define pg_attribute_cold and pg_attribute_hot macros

For compilers supporting __has_attribute and __has_attribute (hot/cold).

__has_attribute is supported on gcc >= 5, clang >= 2.9 and icc >= 17.

A followup commit will implement some usages of these macros.

Author: David Rowley
Reviewed-by: Andres Freund, Peter Eisentraut
Discussion: https://postgr.es/m/CAApHDvrVpasrEzLL2er7p9iwZFZ%3DJj6WisePcFeunwfrV0js_A%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/697e1d02f53f985992a4f479b0b08fca5c272c6c

Modified Files
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src/include/c.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)