pgsql: Make some use of anonymous unions [reloptions]

Make some use of anonymous unions [reloptions]

In the spirit of commit 4b7e6c73b0df and following, which see for more
details; it appears to have been quite an uncontroversial C11 feature to
use and it makes the code nicer to read.

This commit changes the relopt_value struct.

Author: Peter Eisentraut <peter(at)eisentraut(dot)org>
Author: Álvaro Herrera <alvherre(at)kurilemu(dot)de>
Note: Yes, this was written twice independently.
Discussion: https://postgr.es/m/202601192106.zcdi3yu2gzti@alvherre.pgsql

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/69f98fce5bfb82260c66bdae88b6293146cf79ec

Modified Files
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src/backend/access/common/reloptions.c | 38 +++++++++++++++++-----------------
src/include/access/reloptions.h | 2 +-
2 files changed, 20 insertions(+), 20 deletions(-)