nnesse/minwin-gcc-5-2: A patched gcc 5.2 enabling a new 'minwin' target that does not link to the Microsoft C library.

Niels Nesse eb72d50f44 Import gcc 5.2.0 from tarball		9 lat temu
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crc32.go	eb72d50f44 Import gcc 5.2.0 from tarball	9 lat temu
crc32_amd64x.go	eb72d50f44 Import gcc 5.2.0 from tarball	9 lat temu
crc32_generic.go	eb72d50f44 Import gcc 5.2.0 from tarball	9 lat temu
crc32_test.go	eb72d50f44 Import gcc 5.2.0 from tarball	9 lat temu