Fix test 1175 by passing the source root directory (was: tests).
Before this patch this caused silent Perl warnings and returning success
without executing the tests, due to:
```
readline() on closed filehandle $f at ../../tests/test1175.pl line 55.
readline() on closed filehandle $f at ../../tests/test1175.pl line 39.
```
Running the test revealed these issues:
```
CURLE_FUNCTION_NOT_FOUND is not in libcurl-errors.md
CURLE_HTTP_POST_ERROR is not in libcurl-errors.md
CURLE_TELNET_OPTION_SYNTAX is not in libcurl-errors.md
CURLM_CALL_MULTI_SOCKET is not in libcurl-errors.md
```
Apply fixes:
- mark `CURLE_FUNCTION_NOT_FOUND` deprecated by 7.53.0
- mark `CURLE_HTTP_POST_ERROR` deprecated by 7.56.0
- mark `CURLE_TELNET_OPTION_SYNTAX` deprecated by 7.78.0
- document `CURLM_CALL_MULTI_SOCKET` as a synonym for
`CURLM_CALL_MULTI_PERFORM`
- test1477: exclude `CURLM_CALL_MULTI_SOCKET`.
But, these weren't officially deprecated. It may need more updates
to reflect that in other places, or fix the issues differently.
Follow-up to 66ec950004#12424
Follow-up to 74f441c6d3#4628
Cherry-picked from #17877Closes#17880
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