visualc, cope with `bool' and `isnan()' in visual studio 2015

now they have isnan(),
  (presumably in math.h)

now they have a C99 `bool',
  (maybe even though not asked for with <stdbool.h>)

src/include/ngspice/ngspice.h

@@ -177,7 +177,9 @@ extern double x_atanh(double);
 #define fileno _fileno
 #define getcwd _getcwd
 #define chdir _chdir
+#if (_MSC_VER < 1800)
 #define isnan _isnan
+#endif
 #define finite _finite
 #define scalb _scalb
 #define logb _logb
@@ -196,6 +198,12 @@ extern double x_atanh(double);
     static const __int64 global_nan = 0x7ff8000000000000i64;
     #define NAN (*(const double *) &global_nan)
 #endif
+
+// undo a #define bool _Bool in MS Visual Studio 2015
+#if defined(bool)
+#undef bool
+#endif
+
 // warning C4127: Bedingter Ausdruck ist konstant
 #pragma warning(disable: 4127)
 #endif