Should make the test more robust, we were seeing failures in the nightly builds.
When working on a new foo extension, you can now put your tests in the testsuite, set ProjectTags=-foo in mk/build.mk and skip_unless_tag('foo') in the tests.
We will need to do some sort of similarity test to cope with FP differences, but this will at least let us see what differences we need to accommodate.
The name +_0 is a bit dubious.
Saves the test from failing due to small FP differences.
…istent output On some platforms $MAKE == "gmake", so the error messages still didn't match. I made it so that these tests now don't fail in make, but the exit code from GHC is emitted to stderr so we can test it.