COMP: Patch HDF5 compilation issue with mingw and _Float16

This is change is pulled from commit
b09008ea0379e7b113ffdde4402860ba467ace13 upstream.

Define __STDC_WANT_IEC_60559_TYPES_EXT__ before including other headers (InsightSoftwareConsortium#5356)
Some standard headers might implicitly include `float.h`. If that happens
before `__STDC_WANT_IEC_60559_TYPES_EXT__` is defined, the macros that
are needed for the `_Float16` data type (like `FLT16_MAX`) might not be
defined.

That is happening with mingw-w64 headers since the following change: mingw-w64/mingw-w64@b40b6a0

Define `__STDC_WANT_IEC_60559_TYPES_EXT__` before including other headers
in `H5private.h` to make that scenario less likely.

Author: HDF5 Maintainers

Modules/ThirdParty/HDF5/src/CMakeLists.txt

@@ -191,12 +191,6 @@ set(
   CACHE INTERNAL
   "Enable support for non-standard programming language features"
 )
-set(
-  HDF5_ENABLE_NONSTANDARD_FEATURE_FLOAT16
-  ON
-  CACHE INTERNAL
-  "Enable support for _Float16 C datatype"
-)
 set(
   HDF5_ENABLE_SUBFILING_VFD
   OFF

Modules/ThirdParty/HDF5/src/itkhdf5/src/H5private.h

@@ -20,6 +20,11 @@
 #ifndef H5private_H
 #define H5private_H
 
+/* Define __STDC_WANT_IEC_60559_TYPES_EXT__ for _FloatN support, if available.
+ * Do that before including any other headers in case they include <float.h>
+ * implicitly. */
+#define __STDC_WANT_IEC_60559_TYPES_EXT__
+
 #include "H5public.h" /* Include Public Definitions    */
 
 #include <assert.h>
@@ -33,9 +38,6 @@
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
-
-/* Define __STDC_WANT_IEC_60559_TYPES_EXT__ for _FloatN support, if available */
-#define __STDC_WANT_IEC_60559_TYPES_EXT__
 #include <float.h>
 #include <math.h>