pgsql: Call pgwin32_signal_initialize() in postmaster as well.

Call pgwin32_signal_initialize() in postmaster as well.

This was an oversight in 07bf3785099. While it does reduce the benefit of the
simplification due to that commit, it still seems like a win to me.

It seems like it might be a good idea to have a function mirroring
InitPostmasterChild() / InitStandaloneProcess() for postmaster in miscinit.c
to make it easier to keep initialization between the three possible
environment in sync.

Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20210805214109.lzfk3r3ae37bahmv@alap3.anarazel.de

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/0de13bbc47d19c95de132cc85c341fdab079c170

Modified Files
--------------
src/backend/postmaster/postmaster.c | 7 +++++++
1 file changed, 7 insertions(+)