[patch] Make std::tr1::shared_ptr thread-safe.

[Paolo Carlini]

Hi Jonathan,

>I've also changed some tests so they use "dg-excess-errors" instead of
>multiple "dg-error" lines which need their line numbers kept in sync.
>  
>
I'm not sure that using dg-excess-errors is an improvement, because I
don't think
such testcases qualify as special cases per:

    http://gcc.gnu.org/wiki/HowToPrepareATestcase 

>OK to commit to mainline and 4.0 (assuming 4.0 tests also pass) ?
>  
>
Otherwise, ok with me, Jonathan: as usual, please allow all the
maintainers to
comment before checking-in, say wait at least a couple of days.

Paolo.