[CM] Windows compatibility issues with recent s7 code

[jinser]

Dear all,

I'm working on building s7 on Windows (MSYS) and encountered several
compatibility issues. Just wanted to share what I found:

1. Overflow checking in opt_i_add_any_f: The implementation has issues
- add_overflow requires HAVE_OVERFLOW_CHECK macro to be defined, and
cur_sc variable is not in scope (undefined), causing compilation
errors.

2. clock_gettime: This function and <time.h> clock constants aren't
available in MinGW/MSYS (non-posix) environment.

3. uname: The <sys/utsname.h> header and uname() function aren't
available on Windows (non-posix) systems. (I am trying to implement it
in windows api
at https://github.com/NixOS/nixpkgs/blob/744a390d6d3a142bc850e16e86685760084f4099/pkgs/by-name/s7/s7/0001-fix-uname-in-windows.patch
btw)

4. Extra slashify_table assignment: There's a duplicate line assigning
the same array element.

These are just FYI - I've made local fixes by removing these code for
my Windows build.

--
regards,
Jinser Kafka.