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

contrib/cube/cube.c

@@ -8,7 +8,6 @@
 
 #include "postgres.h"
 
-#include <float.h>
 #include <math.h>
 
 #include "access/gist.h"

contrib/jsonb_plperl/jsonb_plperl.c

@@ -1,6 +1,5 @@
 #include "postgres.h"
 
-#include <float.h>
 #include <math.h>
 
 /* Defined by Perl */

contrib/tsm_system_time/tsm_system_time.c

@@ -24,9 +24,6 @@
 
 #include "postgres.h"
 
-#ifdef _MSC_VER
-#include <float.h>				/* for _isnan */
-#endif
 #include <math.h>
 
 #include "access/relscan.h"

src/backend/access/gist/gistproc.c

@@ -17,7 +17,6 @@
  */
 #include "postgres.h"
 
-#include <float.h>
 #include <math.h>
 
 #include "access/gist.h"

src/backend/access/gist/gistutil.c

@@ -13,7 +13,6 @@
  */
 #include "postgres.h"
 
-#include <float.h>
 #include <math.h>
 
 #include "access/gist_private.h"

src/backend/access/tablesample/bernoulli.c

@@ -24,9 +24,6 @@
 
 #include "postgres.h"
 
-#ifdef _MSC_VER
-#include <float.h>				/* for _isnan */
-#endif
 #include <math.h>
 
 #include "access/hash.h"

src/backend/access/tablesample/system.c

@@ -24,9 +24,6 @@
 
 #include "postgres.h"
 
-#ifdef _MSC_VER
-#include <float.h>				/* for _isnan */
-#endif
 #include <math.h>
 
 #include "access/hash.h"

src/backend/optimizer/path/costsize.c

@@ -71,9 +71,6 @@
 
 #include "postgres.h"
 
-#ifdef _MSC_VER
-#include <float.h>				/* for _isnan */
-#endif
 #include <math.h>
 
 #include "access/amapi.h"

src/backend/utils/adt/arrayfuncs.c

@@ -15,9 +15,6 @@
 #include "postgres.h"
 
 #include <ctype.h>
-#ifdef _MSC_VER
-#include <float.h>				/* for _isnan */
-#endif
 #include <math.h>
 
 #include "access/hash.h"

src/backend/utils/adt/datetime.c

@@ -15,7 +15,6 @@
 #include "postgres.h"
 
 #include <ctype.h>
-#include <float.h>
 #include <limits.h>
 #include <math.h>
 

src/backend/utils/adt/int8.c

@@ -14,7 +14,6 @@
 #include "postgres.h"
 
 #include <ctype.h>
-#include <float.h>				/* for _isnan */
 #include <limits.h>
 #include <math.h>
 

src/backend/utils/adt/nabstime.c

@@ -17,7 +17,6 @@
 #include "postgres.h"
 
 #include <ctype.h>
-#include <float.h>
 #include <limits.h>
 #include <math.h>
 #include <time.h>

src/backend/utils/adt/orderedsetaggs.c

@@ -14,7 +14,6 @@
  */
 #include "postgres.h"
 
-#include <float.h>
 #include <math.h>
 
 #include "catalog/pg_aggregate.h"

src/backend/utils/adt/selfuncs.c

@@ -98,7 +98,6 @@
 #include "postgres.h"
 
 #include <ctype.h>
-#include <float.h>
 #include <math.h>
 
 #include "access/brin.h"

src/backend/utils/adt/timestamp.c

@@ -17,7 +17,6 @@
 
 #include <ctype.h>
 #include <math.h>
-#include <float.h>
 #include <limits.h>
 #include <sys/time.h>
 

src/backend/utils/misc/help_config.c

@@ -16,7 +16,6 @@
  */
 #include "postgres.h"
 
-#include <float.h>
 #include <limits.h>
 #include <unistd.h>
 

src/include/port/win32_port.h

@@ -502,7 +502,14 @@ typedef unsigned short mode_t;
 #define W_OK 2
 #define R_OK 4
 
+/*
+ * isinf() and isnan() should per spec be in <math.h>, but MSVC older than
+ * 2013 does not have them there.  It does have _fpclass() and _isnan(), but
+ * they're in <float.h>, so include that here even though it means float.h
+ * percolates to our whole tree.  Recent versions don't require any of this.
+ */
 #if (_MSC_VER < 1800)
+#include <float.h>
 #define isinf(x) ((_fpclass(x) == _FPCLASS_PINF) || (_fpclass(x) == _FPCLASS_NINF))
 #define isnan(x) _isnan(x)
 #endif

src/interfaces/ecpg/ecpglib/data.c

@@ -3,7 +3,6 @@
 #define POSTGRES_ECPG_INTERNAL
 #include "postgres_fe.h"
 
-#include <float.h>
 #include <math.h>
 
 #include "ecpgtype.h"

src/interfaces/ecpg/ecpglib/execute.c

@@ -16,7 +16,6 @@
 #define POSTGRES_ECPG_INTERNAL
 #include "postgres_fe.h"
 
-#include <float.h>
 #include <math.h>
 
 #include "catalog/pg_type_d.h"

src/interfaces/ecpg/pgtypeslib/datetime.c

@@ -4,7 +4,6 @@
 
 #include <time.h>
 #include <ctype.h>
-#include <float.h>
 #include <limits.h>
 
 #include "extern.h"

src/interfaces/ecpg/pgtypeslib/timestamp.c

@@ -4,7 +4,6 @@
 #include "postgres_fe.h"
 
 #include <time.h>
-#include <float.h>
 #include <limits.h>
 #include <math.h>
 

src/port/rint.c

@@ -12,7 +12,6 @@
  */
 #include "c.h"
 
-#include <float.h>
 #include <math.h>
 
 /*

src/port/snprintf.c

@@ -33,9 +33,6 @@
 #include "c.h"
 
 #include <ctype.h>
-#ifdef _MSC_VER
-#include <float.h>				/* for _isnan */
-#endif
 #include <limits.h>
 #include <math.h>
 #ifndef WIN32

src/test/regress/regress.c

@@ -16,7 +16,6 @@
 
 #include "postgres.h"
 
-#include <float.h>
 #include <math.h>
 #include <signal.h>