Printing debugging info by defining MICROPY_DEBUG_VERBOSE expects
a definition of the DEBUG_printf function which is readily available
in printf.c so include that file in the build. Before this patch
one would have to manually provide such definition which is tedious.
For the msvc port disable MICROPY_USE_INTERNAL_PRINTF though: the
linker provides no (easy) way to replace printf with the custom
version as defined in printf.c.
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