SEL_NL is different between Windows and Unix; move it out into the

platform-specific header files.

[originally from svn r2043]

winstuff.h

@@ -64,6 +64,11 @@ GLOBAL HINSTANCE hinst;
  */
 #define SELECTION_NUL_TERMINATED 1
 
+/*
+ * On Windows, copying to the clipboard terminates lines with CRLF.
+ */
+#define SEL_NL { 13, 10 }
+
 /*
  * Exports from winctrls.c.
  */