add missing ei_atan2 without painfull warnings

Eigen/src/Core/MathFunctions.h

diff --git a/Eigen/src/Core/MathFunctions.h b/Eigen/src/Core/MathFunctions.h
index 3527042..4d0d0f0 100644
--- a/Eigen/src/Core/MathFunctions.h
+++ b/Eigen/src/Core/MathFunctions.h
@@ -63,6 +63,7 @@
 inline int ei_log(int)  { ei_assert(false); return 0; }
 inline int ei_sin(int)  { ei_assert(false); return 0; }
 inline int ei_cos(int)  { ei_assert(false); return 0; }
+inline int ei_atan2( int , int  ) { ei_assert(false); return 0; }
 inline int ei_pow(int x, int y)
 {
   int res = 1;
@@ -117,6 +118,7 @@
 inline float ei_log(float x)   { return std::log(x); }
 inline float ei_sin(float x)   { return std::sin(x); }
 inline float ei_cos(float x)   { return std::cos(x); }
+inline float ei_atan2( float y, float x ) { return std::atan2(y,x); }
 inline float ei_pow(float x, float y)  { return std::pow(x, y); }
 
 template<> inline float ei_random(float a, float b)
@@ -165,6 +167,7 @@
 inline double ei_log(double x)   { return std::log(x); }
 inline double ei_sin(double x)   { return std::sin(x); }
 inline double ei_cos(double x)   { return std::cos(x); }
+inline double ei_atan2( double y, double x ) { return std::atan2(y,x); }
 inline double ei_pow(double x, double y) { return std::pow(x, y); }
 
 template<> inline double ei_random(double a, double b)
@@ -211,6 +214,7 @@
 inline std::complex<float> ei_exp(std::complex<float> x)  { return std::exp(x); }
 inline std::complex<float> ei_sin(std::complex<float> x)  { return std::sin(x); }
 inline std::complex<float> ei_cos(std::complex<float> x)  { return std::cos(x); }
+inline std::complex<float> ei_atan2(std::complex<float> , std::complex<float> )  { ei_assert(false); return 0; }
 
 template<> inline std::complex<float> ei_random()
 {
@@ -247,6 +251,7 @@
 inline std::complex<double> ei_exp(std::complex<double> x)  { return std::exp(x); }
 inline std::complex<double> ei_sin(std::complex<double> x)  { return std::sin(x); }
 inline std::complex<double> ei_cos(std::complex<double> x)  { return std::cos(x); }
+inline std::complex<double> ei_atan2(std::complex<double> , std::complex<double> )  { ei_assert(false); return 0; }
 
 template<> inline std::complex<double> ei_random()
 {
@@ -285,6 +290,7 @@
 inline long double ei_log(long double x)   { return std::log(x); }
 inline long double ei_sin(long double x)   { return std::sin(x); }
 inline long double ei_cos(long double x)   { return std::cos(x); }
+inline long double ei_atan2( long double y, long double x ) { return std::atan2(y,x); }
 inline long double ei_pow(long double x, long double y)  { return std::pow(x, y); }
 
 template<> inline long double ei_random(long double a, long double b)