Finished review/fixes of Math and Miscellaneous categories of functions and macros.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@52743 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/math.h

@@ -6,10 +6,23 @@
 // Licence:     wxWindows license
 /////////////////////////////////////////////////////////////////////////////
 
+/** @ingroup group_funcmacro_math */
+//@{
+
 /**
-Returns a non-zero value if @a x is neither infinite nor NaN (not a number),
-returns 0 otherwise.
+    Returns a non-zero value if @a x is neither infinite nor NaN (not a
+    number), returns 0 otherwise.
+
+    @header{wx/math.h}
 */
 int wxFinite(double x);
 
+/**
+    Returns a non-zero value if x is NaN (not a number), returns 0 otherwise.
+
+    @header{wx/math.h}
+*/
+bool wxIsNaN(double x);
+
+//@}