pgsql: More float test and portability fixes.

More float test and portability fixes.

Avoid assuming exact results in tstypes test; some platforms vary.
(per buildfarm members eulachon, danio, lapwing)

Avoid dubious usage (inherited from upstream) of bool parameters to
copy_special_str, to see if this fixes the mac/ppc failures (per
buildfarm members prariedog and locust). (Isolated test programs on a
ppc mac don't seem to show any other cause that would explain them.)

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/da6520be7f946f5f0f8fe46c34e303d1d36ee080

Modified Files
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src/common/d2s.c | 2 +-
src/common/f2s.c | 2 +-
src/test/regress/expected/tstypes.out | 66 ++++++++++++++++++-----------------
src/test/regress/sql/tstypes.sql | 3 ++
4 files changed, 39 insertions(+), 34 deletions(-)