[PATCH 1/3] conform: Add C23 checks for <stdint.h>

[Joseph Myers]

This is missing at least the macro __STDC_VERSION_STDINT_H__.  (My 
inclination is that we should define the header version macros in glibc 
once all the C23 features are done - *not* the same as all the new symbols 
in each respective header being implemented, since the macros also cover 
changes to semantics of existing symbols.  But conform/ baselines aren't 
supposed to depend on what features are or aren't implemented in glibc.)

-- 
Joseph S. Myers
josmyers@redhat.com