pgsql: Suppress some compiler warnings in recent commits.

Suppress some compiler warnings in recent commits.

Older versions of gcc tend to throw "variable might be clobbered by
`longjmp' or `vfork'" warnings whenever a variable is assigned in more than
one place and then used after the end of a PG_TRY block. That's reasonably
easy to work around in execute_extension_script, and the overhead of
unconditionally saving/restoring the GUC variables seems unlikely to be a
serious concern.

Also clean up logic in ATExecValidateConstraint to make it easier to read
and less likely to provoke "variable might be used uninitialized in this
function" warnings.

Branch
------
master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=375e5b0a687570eb41fb9e9fda9e5d6992fccffa

Modified Files
--------------
src/backend/commands/extension.c | 31 ++++++++++++-------------------
src/backend/commands/tablecmds.c | 37 ++++++++++++++++++-------------------
2 files changed, 30 insertions(+), 38 deletions(-)