Here is yet another attempt at a patch to auto-generate SIMD clones for 
functions that already have the "declare target" attribute.  This 
version v4 is derived from the previous v2 version, since v3 seemed to 
be a dead end.

I have added conditionals to restrict the auto-generation at -O2 to the 
offload compiler, and extended the syntax of the 
-fopenmp-target-simd-clone to allow explicit control over whether it 
applies to host, target, or both -- this primarily to allow better test 
coverage.  I've added infrastructure to support testing on the offload 
compiler, added new test cases, and reworked the existing test cases to 
scan for interesting things written to the dump file instead of 
examining the .s output.

I hope it is not too late to consider this patch given that I've been 
trying to get this feature in for months already.  Also, I kind of got 
caught in the Sphinx churn last week, relating to the documentation 
parts of this patch.  :-(  I understand that if this patch is accepted I 
am also on the hook to come up with a further patch to try to GC unused 
clones after vectorization; I haven't started on that piece yet.

-Sandra