pgsql: Fix xl_heap_lock WAL record field's data type.

Fix xl_heap_lock WAL record field's data type.

Make xl_heap_lock's infobits_set field of type uint8, not int8.  Using
int8 isn't appropriate given that the field just holds status bits.
This fixes an oversight in commit 0ac5ad5134.

In passing rename the nearby TransactionId field to "xmax" to make
things consistency with related records, such as xl_heap_lock_updated.

Deliberately avoid a bump in XLOG_PAGE_MAGIC.  No backpatch, either.

Author: Peter Geoghegan <pg@bowt.ie>
Discussion: https://postgr.es/m/CAH2-WzkCd3kOS8b7Rfxw7Mh1_6jvX=Nzo-CWR1VBTiOtVZkWHA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/e944063294fb9e85190f03948f5ce20331231e2f

Modified Files
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src/backend/access/heap/heapam.c       | 6 +++---
src/backend/access/rmgrdesc/heapdesc.c | 4 ++--
src/include/access/heapam_xlog.h       | 6 +++---
3 files changed, 8 insertions(+), 8 deletions(-)