- `websocket.c`: use `Sleep()` on Windows.
`sleep()` and `unistd.h` are not available in MSVC.
- `http2-upload.c`: use local `gettimeofday()` implementation when
compiled with MSVC.
(Alternate solution is to disable the trace function for MSVC.)
Public domain code copied and adapted from libssh2:
e973493f99/src/misc.c (L719-L743)
- silence compiler warning for deprecated `inet_addr()`.
Also drop duplicate winsock2 include.
```
curl\docs\examples\externalsocket.c(125,32): error C2220: the following warning is treated as an error [curl\bld\docs\examples\curl-example-externalsocket.vcxproj]
curl\docs\examples\externalsocket.c(125,32): warning C4996: 'inet_addr': Use inet_pton() or InetPton() instead or define _WINSOCK_DEPRECATED_NO_WARNINGS to disable deprecated API warnings [curl\bld\docs\examples\curl-example-e
```
Ref: https://github.com/curl/curl/actions/runs/9227337318/job/25389073450#step:4:95
- silence an MSVC compiler warning. This is in conflict with `checksrc`
rules, so silence the rule in favour of the warning-free C syntax.
```
curl\docs\examples\multi-legacy.c(152,1): error C2220: the following warning is treated as an error [curl\bld\docs\examples\curl-example-multi-legacy.vcxproj]
curl\docs\examples\multi-legacy.c(152,1): warning C4706: assignment within conditional expression [curl\bld\docs\examples\curl-example-multi-legacy.vcxproj]
```
Ref: https://github.com/curl/curl/actions/runs/9227337318/job/25389073450#step:4:226
- do not use `sys/time.h` and `unistd.h` in Windows builds.
Some of these includes look unnecessary. Subject to another PR.
Cherry-picked from #13766Closes#13771
