Mark R_DefCallbacks as Windows-only in R_ext/RStartup.h.

git-svn-id: https://svn.r-project.org/R/trunk@89069 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: luke

src/include/R_ext/RStartup.h

@@ -146,7 +146,9 @@ int R_DefParamsEx(Rstart, int);
        only supports version 0 of the structure.
     */
 void R_SetParams(Rstart);
+#ifdef Win32
 void R_DefCallbacks(Rstart, int);
+#endif
 void R_SetWin32(Rstart);
 void R_SizeFromEnv(Rstart);
 void R_common_command_line(int *, char **, Rstart);