pgsql: Tidy up XLogSource code in xlog.c.

Tidy up XLogSource code in xlog.c.

This commit replaces 0 used as an initial value of XLogSource variable,
with XLOG_FROM_ANY. Also this commit changes those variable so that
XLogSource instead of int is used as the type for them. These changes
are for code readability and debugger-friendliness.

Author: Kyotaro Horiguchi
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/20200227.124830.2197604521555566121.horikyota.ntt@gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/71e0d0a73773b3985db658d3c5366ce5ceef76ae

Modified Files
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src/backend/access/transam/xlog.c | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)