pgsql: Rename tuplesort.c's SortTuple.tupindex field.

Rename tuplesort.c's SortTuple.tupindex field.

Rename the "tupindex" field from tuplesort.c's SortTuple struct to
"srctape", since it can only ever be used to store a source/input tape
number when merging external sort runs.  This has been the case since
commit 8b304b8b72b, which removed replacement selection sort from
tuplesort.c.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d8cd68c8d472292ef8943a765bd1c69c0d4d61d8

Modified Files
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src/backend/utils/sort/tuplesort.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)