sc_sock: fix compiler warnings for Windows

[svladykin]

• Fix types
• Use pragma only for MSVC
• Drop C11 anonymous union
• Use INVALID_SOCKET instead of SOCKET_ERROR where appropriate

[codecov]

Codecov Report

Merging #127 (e0188e7) into master (e7134b7) will not change coverage.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #127   +/-   ##
=======================================
  Coverage   99.81%   99.81%           
=======================================
  Files          21       21           
  Lines        2195     2195           
  Branches      388      388           
=======================================
  Hits         2191     2191           
  Misses          1        1           
  Partials        3        3           

Files	Coverage Δ
socket/sc_sock.c	99.19% <100.00%> (ø)

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e7134b7...e0188e7. Read the comment docs.

[tezc]

Hey @svladykin, hope you are doing well! Any idea why we don't see these warnings on CI? Maybe we need to compile release version to see it?

[svladykin]

I guess this is because we don't have any of these flags enabled for Windows:

if (NOT CMAKE_C_COMPILER_ID MATCHES "MSVC")
    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -g -Wall -Wextra -pedantic -pthread -Werror")
endif ()

Not sure if they will actually work for MSVC though.

I experimented with cross-compilation for Windows on Linux:

• tried Zig CC (uses Clang inside) and it can compile the code but fails to link, but this is enough to produce all the warnings;
• was able to successfully cross-compile a dll with Mingw (uses Gcc inside).

This PR is based on Mingw and Zig CC output.

[tezc]

Ok, I'll take a look that later.