LibM: Add exp2() and exp2f()

Libraries/LibM/math.cpp

@@ -279,6 +279,16 @@ float expf(float exponent)
     return (float)exp(exponent);
 }
 
+double exp2(double exponent)
+{
+    return pow(2.0, exponent);
+}
+
+float exp2f(float exponent)
+{
+    return pow(2.0f, exponent);
+}
+
 double cosh(double x)
 {
     double exponentiated = exp(-x);

Libraries/LibM/math.h

@@ -74,6 +74,8 @@ double fmod(double, double);
 float fmodf(float, float);
 double exp(double);
 float expf(float);
+double exp2(double);
+float exp2f(float);
 double frexp(double, int* exp);
 float frexpf(float, int* exp);
 double log(double);