adjust pointer size from 4 to 8 bytes in x86_64 site config

SVN-Revision: 17845

include/site/x86_64-linux

@@ -25,4 +25,4 @@ ac_cv_sizeof_unsigned_int=4
 ac_cv_sizeof_unsigned_long=8
 ac_cv_sizeof_unsigned_long_long=8
 ac_cv_sizeof_unsigned_short=2
-ac_cv_sizeof_void_p=4
+ac_cv_sizeof_void_p=8