Avoid name clashes with symbols that leak from system headers

Signed-off-by: malc <av1474@comtv.ru>
diff --git a/elf.h b/elf.h
index b042002..11674d7 100644
--- a/elf.h
+++ b/elf.h
@@ -454,7 +454,9 @@
 #define R_PPC_SECTOFF_HI	35
 #define R_PPC_SECTOFF_HA	36
 /* Keep this the last entry.  */
+#ifndef R_PPC_NUM
 #define R_PPC_NUM		37
+#endif
 
 /* ARM specific declarations */