[asan] Emit GIMPLE directly, small cleanups

[Eric Botcazou]

> Eric, Rainer, what do you think of the other two options I outlined in
> my earlier message?
> 
> 1- Copy the upstream testsuite into gcc/testsuite/asan.  This gives us
> the flexibility of adding new tests as the GCC implementation matures.
> 
> 2- Deal with libasan as we deal with zlib/boehm-gc.
> 
> I prefer option #1, personally.

I feel a bit umconfortable saying this given the gcc/testsuite/ada/acats 
precedent, but I don't think we should import foreing testsuites into 
gcc/testsuite, unless they are adapted to our harness.  I don't think we
want to run again into the issues we had with acats (Rainer puts a lot of 
efforts to clean up the mess here).

-- 
Eric Botcazou