message: Replace the non standard M_PI with a constant
diff: #include <list>
  #include <iostream>
  -#ifdef _WIN32
  -#if !defined(_USE_MATH_DEFINES)
  -#define _USE_MATH_DEFINES // For M_PI.
  -#endif // !defined(_USE_MATH_DEFINES)
  -#endif // _WIN32
  -
  #include <math.h>
  #include "flatbuffers/idl.h"
  namespace flatbuffers {
  +const double kPi = 3.14159265358979323846;
  +
  const char *const kTypeNames[] = {
  #define FLATBUFFERS_TD(ENUM, IDLTYPE, \
  CTYPE, JTYPE, GTYPE, NTYPE, PTYPE) \
  @@ -1272,8 +1268,8 @@ CheckedError Parser::ParseSingleValue(Value &e) {
  auto x = strtod(e.constant.c_str(), nullptr); \
  e.constant = NumToString(op); \
  }
  - FLATBUFFERS_FN_DOUBLE("deg", x / M_PI * 180);
  - FLATBUFFERS_FN_DOUBLE("rad", x * M_PI / 180);
  + FLATBUFFERS_FN_DOUBLE("deg", x / kPi * 180);
  + FLATBUFFERS_FN_DOUBLE("rad", x * kPi / 180);
  FLATBUFFERS_FN_DOUBLE("sin", sin(x));
  FLATBUFFERS_FN_DOUBLE("cos", cos(x));
  FLATBUFFERS_FN_DOUBLE("tan", tan(x));
  