Documentation bugs in 2.53

[povey]

1. Can't view the node AC_LIBOBJ vs. LIBOBJ.  info doesn't like the 
full-stop in vs.  This is pretty important as users really need to know
this info.

2. The example for AC_CONFIG_COMMANDS_PRE shows the old unsafe way of
   accessing LIBOBJ as an example!

3. The URL for reporting bugs via gnats doesn't work!


-- 
Cheers.
Dean.