Switched @NULL back to (the appropriate) @NUL and added NUL command to Doxygen.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@57859 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/doxygen/Doxyfile_inc

@@ -111,6 +111,7 @@ ALIASES += header{1}="Include file:\n \verbatim #include <\1> \endverbatim"
 ALIASES += true="<span class='literal'>true</span>"
 ALIASES += false="<span class='literal'>false</span>"
 ALIASES += NULL="<span class='literal'>NULL</span>"
+ALIASES += NUL="<span class='literal'>NUL</span>"
 
 # NOTE: these are important as you can't write in the docs
 #       just #ifdef since the # character is used by Doxygen

interface/wx/wxcrt.h

@@ -91,7 +91,7 @@ wxArrayString wxStringTokenize(const wxString& string,
 
     This function copies the source string @a src to the destination buffer @a
     dst of size @a n without overflowing the buffer and ensuring that it is
-    always @NULL-terminated.
+    always @NUL-terminated.
 
     Example of use:
     @code
@@ -121,7 +121,7 @@ wxArrayString wxStringTokenize(const wxString& string,
     @param dst
         Destination buffer of size (greater or) equal to @a n.
     @param src
-        @NULL-terminated source string.
+        @NUL-terminated source string.
     @param n
         The size of the destination buffer.
     @return