[PATCH 2/5]: Use pointer_map in structalias

[Paolo Bonzini]

>>  /* Insert ID as the variable id for tree T in the hashtable.  */
>>  
> Need to update comment.

But it is still a hash table :-)  (I see your point of course).

>>  /* Find the variable info for tree T in VI_FOR_TREE.  If T does not
>>     exist in the hash table, return false, otherwise, return true and
>>     set *VI to the varinfo we found.  */
>>  
> Likewise.
> 
> Any noticeable compile-time differences?

I had to run the tests manually because Fortran was broken, so I don't 
know; my script was comparing the compile-time for a full bootstrap with 
the compile-time up to libgfortran.

Paolo