Extend PTS arithmetic to allow pointing to "one past" the end of a shared array

[GoogleCodeExporter]

Steve's comments moved from issue 106:

1. Is pointing to one element past the end of a shared array object valid (as 
it is for local objects by ISO/IEC 9899 6.5.6 8-9)?  If so, we should be sure 
that we get the expected behavior for those as well.  Note that this is a much 
larger change, as a lot of the spec assumes that any valid non-null 
pointer-to-shared points to an object.

This is trivial to express.  The existing equations in 6.4.2 3 define the exact 
behavior of upc_threadof() and upc_phaseof().  My proposal in comment 13 
suffices to define the behavior of upc_addrfield(), and can be trivially 
tweaked to define the local address as well.  Since you can't do 
pointer-to-shared arithmetic on generic pointers-to-shared, nor on 
pointers-to-shared whose referenced type is incomplete, we don't need to worry 
about what "one past" means in those cases, and it is well-defined for all 
others.

Original issue reported on code.google.com by danbonachea on 1 Mar 2013 at 6:25