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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BigDecimal.h	eb72d50f44 Import gcc 5.2.0 from tarball	9 lat temu
BigInteger.h	eb72d50f44 Import gcc 5.2.0 from tarball	9 lat temu
MathContext.h	eb72d50f44 Import gcc 5.2.0 from tarball	9 lat temu
RoundingMode.h	eb72d50f44 Import gcc 5.2.0 from tarball	9 lat temu