pgsql: Make unconstify and unvolatize use StaticAssertVariableIsOfTypeM

Make unconstify and unvolatize use StaticAssertVariableIsOfTypeMacro

The unconstify and unvolatize macros had an almost identical assertion
as was already defined in StaticAssertVariableIsOfTypeMacro, only it
had a less useful error message and didn't have a sizeof fallback.

Author: Jelte Fennema-Nio <postgres@jeltef.nl>
Discussion: /messages/by-id/CAGECzQR21OnnKiZO_1rLWO0-16kg1JBxnVq-wymYW0-_1cUNtg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/258248d0bdbf1b1818e2c6a157b17227fd000d76

Modified Files
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src/include/c.h | 13 +++----------
1 file changed, 3 insertions(+), 10 deletions(-)