pgsql: Silence warning in older versions of Valgrind

Silence warning in older versions of Valgrind

Due to misunderstanding on my part, commit 235328ee4 did not go far
enough to silence older versions of Valgrind. For those, it was the bit
scan that was problematic, not the subsequent bit-masking operation. To
fix, use the unaligned path for the trailing bytes. Since we don't have
a bit scan here anymore, also remove some comments and endian-specific
coding around that.

Reported-by: Anton A. Melnikov <a(dot)melnikov(at)postgrespro(dot)ru>
Discussion: https://postgr.es/m/f3aa2d45-3b28-41c5-9499-a1bc30e0f8ec@postgrespro.ru
Backpatch-through: 17

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/0600d276d485a8222eb6b571b08889c9f539e86f

Modified Files
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src/include/common/hashfn_unstable.h | 26 +++-----------------------
1 file changed, 3 insertions(+), 23 deletions(-)