timg.cc: define __STDC_FORMAT_MACROS if undefined

[barracuda156]

Change of the header to <cinttypes> fixes the build with GCC, but some older clangs (and possibly other compilers) need __STDC_FORMAT_MACROS even then, so just define it to be on the safe side.

[hzeller]

This does look like a somewhat old requirement, removed in around 2013 https://sourceware.org/git/?p=glibc.git;a=commit;h=1ef74943ce2f114c78b215af57c2ccc72ccdb0b7

Can you add a comment saying with which compiler version you encountered an issue ? This makes it easier to keep track of and possibly decide when to remove the workaround in the future.

[barracuda156]

@hzeller The issue is conditional on the OS, not only compiler. I use gcc14 now, but I know that the issue has been observed with clangs on older macOS version as well.
It appears from C++ online documentation that the issue may affect some other systems (it is not exclusive to macOS, otherwise that would probably be mentioned), but I only use macOS.

P. S. gcc does not need this macro when C++ header cinttypes is used. But needs with the C header.

[barracuda156]

@hzeller Thanks for merging!