pgsql: Rethink how to get float.h in old Windows API for isnan/isinf

Rethink how to get float.h in old Windows API for isnan/isinf

We include <float.h> in every place that needs isnan(), because MSVC
used to require it.  However, since MSVC 2013 that's no longer necessary
(cf. commit cec8394b5ccd), so we can retire the inclusion to a
version-specific stanza in win32_port.h, where it doesn't need to
pollute random .c files.  The header is of course still needed in a few
places for other reasons.

I (Álvaro) removed float.h from a few more files than in Emre's original
patch.  This doesn't break the build in my system, but we'll see what
the buildfarm has to say about it all.

Author: Emre Hasegeli
Discussion: https://postgr.es/m/CAE2gYzyc0+5uG+Cd9-BSL7NKC8LSHLNg1Aq2=8ubjnUwut4_iw@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f2c587067a8eb9cf1c8f009262381a6576ba3dd0

Modified Files
--------------
contrib/cube/cube.c                        | 1 -
contrib/jsonb_plperl/jsonb_plperl.c        | 1 -
contrib/tsm_system_time/tsm_system_time.c  | 3 ---
src/backend/access/gist/gistproc.c         | 1 -
src/backend/access/gist/gistutil.c         | 1 -
src/backend/access/tablesample/bernoulli.c | 3 ---
src/backend/access/tablesample/system.c    | 3 ---
src/backend/optimizer/path/costsize.c      | 3 ---
src/backend/utils/adt/arrayfuncs.c         | 3 ---
src/backend/utils/adt/datetime.c           | 1 -
src/backend/utils/adt/int8.c               | 1 -
src/backend/utils/adt/nabstime.c           | 1 -
src/backend/utils/adt/orderedsetaggs.c     | 1 -
src/backend/utils/adt/selfuncs.c           | 1 -
src/backend/utils/adt/timestamp.c          | 1 -
src/backend/utils/misc/help_config.c       | 1 -
src/include/port/win32_port.h              | 7 +++++++
src/interfaces/ecpg/ecpglib/data.c         | 1 -
src/interfaces/ecpg/ecpglib/execute.c      | 1 -
src/interfaces/ecpg/pgtypeslib/datetime.c  | 1 -
src/interfaces/ecpg/pgtypeslib/timestamp.c | 1 -
src/port/rint.c                            | 1 -
src/port/snprintf.c                        | 3 ---
src/test/regress/regress.c                 | 1 -
24 files changed, 7 insertions(+), 35 deletions(-)