Discrepancy in inttypes.h

There is an apparent discrepancy in naming conventions between

     newlib/libc/include/machine/_default_types.h

and

     newlib/libc/include/inttypes.h

The first defines the macro "___int64_t_defined" (with three 
underscores), whereas the second tests for "__int64_t_defined". As a 
consequence, the macros "PRIu64" and friends never get defined. (This 
causes build failures for some of the tests included with the pico-sdk 
[https://github.com/raspberrypi/pico-sdk.git]). There is a file called

     newlib/libc/include/sys/_stdint.h

which translates from the "___" to "__" versions, but somehow that does 
not do the trick. Happy to test more if helpful.

Tested with commit 1b7c72fdcc4bde7520407d2d3364146f04fb8312 as well as 
version 4.4.0.20231231-2 (Ubuntu 24.04.1).