newlib (nano) does not support 64 bit types (neither in stdio nor with
corresponding `PRI*64` macros). With GCC 13.2.1 (as shipped in Ubuntu
24.04.1 LTS), this triggers the following compilation error (even with
`ENABLE_DEBUG == 0`):
sys/matstat/matstat.c:57:21: error: expected ')' before 'PRIu64'
57 | DEBUG("Var: (%" PRIu64 " / (%" PRId32 " - 1)) = %" PRIu64 "\n",
| ^~~~~~
This fixes the issue by falling back to printing 32 bit values when
the `PRIu64` macro is not defined. A `!trunc` is appended when the
64 bit exceeds the range of [0:UINT32_MAX].
