[PATCH, middle-end]: Fix g++.dg/other/vector-compare.C testsuite failure on alpha

[Eric Botcazou]

> Vector compare testcases can't be compiled with 4.7- - vector compares
> are not implemented for C++ there. As observed, BLKmode compare is not
> triggered for alpha in the whole testsuite, as far as release branches
> are concerned.

Then there is no real reason to touch the release branches in my opinion.

The second hunk is OK for mainline (without the now useless label).

-- 
Eric Botcazou