[m-rev.] diff: define MR_is_{nan, infinite, finite} as macros with VS2013

[Julien Fischer]

Define MR_is_{nan,infinite,finite} as macros with VS2013.

This is a follow-up to commit fff5759.  If we are using C99 we define
MR_is_{nan,infinite,finite} as macros.  We should do the same for MSVC version
1800 (VS2013) and onwards and the only reason we didn't already is that MSVC
doesn't define the __STDC_VERSION__ macro appropriately.

runtime/mercury_float.h:
     Define MR_is_{nan,infinite,finite} as macros with MSVC version 1800
     and onwards.

Julien.

diff --git a/runtime/mercury_float.h b/runtime/mercury_float.h
index 7104b0c..376c45b 100644
--- a/runtime/mercury_float.h
+++ b/runtime/mercury_float.h
@@ -213,13 +213,12 @@ MR_Integer MR_hash_float(MR_Float);
  /*
  ** We define MR_is_{nan,infinite,finite} as macros if we support C99
  ** since the resulting code is faster.
+** MSVC also supports these macros (from VS2013 onwards) but it does not
+** set __STDC_VERSION__ appropriately.
+** (1800 is the internal MSVC version number for VS2013.)
  */
-#if __STDC_VERSION__ >= 199901
-    #if defined(MR_USE_SINGLE_PREC_FLOAT)
-        #define MR_is_nan(f) isnanf((f))
-    #else
-        #define MR_is_nan(f) isnan((f))
-    #endif
+#if __STDC_VERSION__ >= 199901 || MR_MSVC >= 1800
+    #define MR_is_nan(f) isnan((f))
  #else
      #define MR_is_nan(f) MR_is_nan_func((f))
  #endif
@@ -228,12 +227,8 @@ MR_Integer MR_hash_float(MR_Float);
  ** See comments for function MR_is_infinite_func in mercury_float.c for the
  ** handling of Solaris here.
  */
-#if __STDC_VERSION__ >= 199901 && !defined(MR_SOLARIS)
-    #if defined(MR_USE_SINGLE_PREC_FLOAT)
-        #define MR_is_infinite(f) isinff((f))
-    #else
-        #define MR_is_infinite(f) isinf((f))
-    #endif
+#if (__STDC_VERSION__ >= 199901 && !defined(MR_SOLARIS)) || MR_MSVC >= 1800
+    #define MR_is_infinite(f) isinf((f))
  #else
      #define MR_is_infinite(f) MR_is_infinite_func((f))
  #endif
@@ -241,7 +236,7 @@ MR_Integer MR_hash_float(MR_Float);
  /*
  ** XXX I don't know whether isfinite works on Solaris or not.
  */
-#if __STDC_VERSION__ >= 199901 && !defined(MR_SOLARIS)
+#if (__STDC_VERSION__ >= 199901 && !defined(MR_SOLARIS)) || MR_MSVC >= 1800
      #define MR_is_finite(f) isfinite((f))
  #else
      #define MR_is_finite(f) (!MR_is_infinite((f)) && !MR_is_nan((f)))