pgsql: Clarify comment for worst-case allocation in quote_literal_cstr(

Clarify comment for worst-case allocation in quote_literal_cstr()

palloc() is invoked with a specific formula for its allocation size in
quote_literal_cstr(). This wastes some memory, but the size is large
enough to cover even the worst-case scenarios.

No explanations were given about the reasons behind these numbers. This
commit adds more documentation about all that.

Author: Steve Chavez <steve(at)supabase(dot)io>
Discussion: https://postgr.es/m/CAGRrpzZ9bToRWS+fAnjxDJrxwZN1QcJ-y1Pn2yg=Hst6rydLtw@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/c36eda259130faf3559b751b9e81a5c7e2bee0d7

Modified Files
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src/backend/utils/adt/quote.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)