Code coverage in Phobos

[Seb via Digitalmars-d]

AFAIK dmd supports the `-cov` flag since quite some time, so I 
would be interested why there's no code coverage bot. There also 
seems to exist at least two external platforms that allow such 
code coverage analyzing [1, 2]. Is this already on your roadmap?

[1] https://github.com/codecov/example-d
[2] https://github.com/ColdenCullen/doveralls/issues/16

Anyways it seems pretty easy to hack something quick&dirty 
together that could be pretty helpful:

```
for f in $(find . -name '*.d' -type f -not -path './c/*'); do 
;fe="${f%.*}"; (cd $(dirname "$f") && rdmd -cov -unittest -main 
"$(basename $f)") && printf "$f " && tail -n1 "$fe".lst | cut -f3 
-d ' ' ; done | sort
```

./algorithm/comparison.d 95%
./algorithm/internal.d no
./algorithm/iteration.d 96%
./algorithm/mutation.d 99%
./algorithm/package.d no
./algorithm/searching.d 97%
./algorithm/setops.d 94%
./algorithm/sorting.d 98%
./array.d 95%
./ascii.d 100%
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./concurrencybase.d 100%
./container/array.d 94%
./container/binaryheap.d 59%
./container/dlist.d 92%
./container/package.d 1%
./container/rbtree.d 94%
./container/slist.d 95%
./container/util.d 100%
./conv.d 94%
./cstream.d 92%
./datetime.d 94%
./demangle.d 0%
./digest/crc.d 100%
./digest/digest.d 72%
./digest/hmac.d 100%
./digest/md.d 100%
./digest/ripemd.d 100%
./digest/sha.d 80%
./encoding.d 66%
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./experimental/allocator/building_blocks/allocator_list.d 81%
./experimental/allocator/building_blocks/bitmapped_block.d 91%
./experimental/allocator/building_blocks/bucketizer.d 48%
./experimental/allocator/building_blocks/fallback_allocator.d 89%
./experimental/allocator/building_blocks/free_list.d 75%
./experimental/allocator/building_blocks/kernighan_ritchie.d 80%
./experimental/allocator/building_blocks/null_allocator.d 56%
./experimental/allocator/building_blocks/package.d no
./experimental/allocator/building_blocks/quantizer.d 69%
./experimental/allocator/building_blocks/region.d 70%
./experimental/allocator/building_blocks/scoped_allocator.d 78%
./experimental/allocator/building_blocks/segregator.d 50%
./experimental/allocator/building_blocks/stats_collector.d 95%
./experimental/allocator/common.d 88%
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./experimental/allocator/showcase.d 100%
./experimental/allocator/typed.d 54%
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