Add public wxDegToRad() and wxRadToDeg() functions.

Define these functions just once in wx/math.h instead of duplicating them in a
dozen of places.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76555 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/math.h

@@ -42,6 +42,30 @@ wxFloat64 wxConvertFromIeeeExtended(const wxInt8 *bytes);
 */
 void wxConvertToIeeeExtended(wxFloat64 num, wxInt8 *bytes);
 
+/**
+    Convert degrees to radians.
+
+    This function simply returns its argument multiplied by @c M_PI/180 but is
+    more readable than writing this expression directly.
+
+    @see wxRadToDeg()
+
+    @since 3.1.0
+ */
+double wxDegToRad(double deg);
+
+/**
+    Convert radians to degrees.
+
+    This function simply returns its argument multiplied by @c 180/M_PI but is
+    more readable than writing this expression directly.
+
+    @see wxDegToRad()
+
+    @since 3.1.0
+ */
+double wxRadToDeg(double rad);
+
 /**
     Small wrapper around round().
 */