pgsql: Switch flags tracking pending interrupts to sig_atomic_t

Switch flags tracking pending interrupts to sig_atomic_t

Those previously used bool, which should be safe on any modern
platforms, however the C standard is clear that it is better to use
sig_atomic_t for variables manipulated in signal handlers.  This commit
adds at the same time PGDLLIMPORT to ClientConnectionLost.

Author: Michael Paquier
Reviewed-by: Tom Lane, Chris Travers, Andres Freund
Discussion: https://postgr.es/m/20180925011311.GD1354@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ba16aade337b16028d1e9e156d83417097c13817

Modified Files
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src/backend/utils/init/globals.c | 10 +++++-----
src/include/miscadmin.h          | 10 +++++-----
2 files changed, 10 insertions(+), 10 deletions(-)