pgsql: Make "pgoff_t" be a typedef not a #define.

Make "pgoff_t" be a typedef not a #define.

There doesn't seem to be any great reason why this has been a macro
rather than a typedef. But doing it like that means our buildfarm
typedef tooling doesn't capture the name as a typedef. That would
result in pgindent glitches, except that we've seemingly kept it
in typedefs.list manually. That's obviously error-prone, so let's
convert it to a typedef now.

Discussion: https://postgr.es/m/1681301.1765742268@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/66b2282b0c2237bccd933804da2e1dd0321ac151

Modified Files
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src/include/port.h | 2 +-
src/include/port/win32_port.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)