pgsql: Change return type of ExceptionalCondition to void and mark it n

Change return type of ExceptionalCondition to void and mark it noreturn

In ancient times, it was thought that this wouldn't work because of
TrapMacro/AssertMacro, but changing those to use a comma operator
appears to work without compiler warnings.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/81107282a5ff1490a0a4ded193cbc61e69cda537

Modified Files
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src/backend/utils/error/assert.c | 7 +------
src/backend/utils/error/elog.c | 8 +-------
src/include/postgres.h | 8 ++++----
3 files changed, 6 insertions(+), 17 deletions(-)