pgsql: struct XmlTableRoutine: use C99 designated initializers

struct XmlTableRoutine: use C99 designated initializers

As in c27f8621eed et al.

Not as critical as other cases we've handled, but I figure if we're
going to add JsonbTableRoutine using TableFuncRoutine, this makes it
easier to jump around the code.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/585025397337281cdce31bf1df2e0868cfbd0b92

Modified Files
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src/backend/utils/adt/xml.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)