[tuples] merge with mainline @137837

[Aldy Hernandez]

I have merged mainline @137837 into the branch.

Jakub reports:

	I don't have a testsuite_summary log from after the PRE commit but
	before this merge, only summary from yesterday.  There are many tests
	fixed (most of them likely because of the PRE merge) and several
	regressions (again, likely culprit will be PRE or invalid gimple PRE is
	upset about), but your merge together with
	http://gcc.gnu.org/ml/gcc-patches/2008-07/msg01066.html bootstrapped
	fine and we can IMHO deal with the regressions tomorrow

Jakub, thanks for testing the merge.

Aldy