Added the function and macro group pages for Doxygen.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@52477 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/doxygen/groups/funcmacro_atomic.h

@@ -0,0 +1,30 @@
+/////////////////////////////////////////////////////////////////////////////
+// Name:        funcmacro_atomic.h
+// Purpose:     Atomic Operation function and macro group docs
+// Author:      wxWidgets team
+// RCS-ID:      $Id: funcmacro_gdi.h 52454 2008-03-12 19:08:48Z BP $
+// Licence:     wxWindows license
+/////////////////////////////////////////////////////////////////////////////
+
+/**
+
+@defgroup group_funcmacro_atomic Atomic Operations
+@ingroup group_funcmacro
+
+When using multi-threaded applications, it is often required to access or
+modify memory which is shared between threads. Atomic integer and pointer
+operations are an efficient way to handle this issue (another, less efficient,
+way is to use a mutex or critical section). A native implementation exists for
+Windows, Linux, Solaris and Mac OS X, for other OS, a wxCriticalSection is used
+to protect the data.
+
+One particular application is reference counting (used by so-called smart
+pointers).
+
+You should define your variable with the type wxAtomicInt in order to apply
+atomic operations to it.
+
+@header{wx/atomic.h}
+
+*/
+