pgsql: Add support for Tcl 9

Add support for Tcl 9

Tcl 9 changed several API functions to take Tcl_Size, which is
ptrdiff_t, instead of int, for 64-bit enablement.  We have to change a
few local variables to be compatible with that.  We also provide a
fallback typedef of Tcl_Size for older Tcl versions.

The affected variables are used for quantities that will not approach
values beyond the range of int, so this doesn't change any
functionality.

Reviewed-by: Tristan Partin <tristan@partin.io>
Discussion: https://www.postgresql.org/message-id/flat/bce0fe54-75b4-438e-b42b-8e84bc7c0e9c%40eisentraut.org

Branch
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REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/07c77803c82bf251b085611f72e2a10ebe8ab51c

Modified Files
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src/pl/tcl/pltcl.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)