Parameters for chown should be signed integers not unsigned

[nicholi]

Fixes #10748

The calls for chown, lchown, fchown, and fchownat (from Mono.Unix.Native.Syscall) are all declared with unsigned integers for the owner and group parameters. This is incorrect.

Directly from the manpage
man 2 chown

...
       int chown(const char *pathname, uid_t owner, gid_t group);
       int fchown(int fd, uid_t owner, gid_t group);
       int lchown(const char *pathname, uid_t owner, gid_t group);

...

       int fchownat(int dirfd, const char *pathname,
                    uid_t owner, gid_t group, int flags);

...
...
       If the owner or group is specified as -1, then that ID is not changed.
...

Emphasis added on the documentation explaining how the parameters can take the value -1, clearly not an unsigned integer. The uid_t struct is not an unsigned integer. I am assuming this was just an oversite on whoever re-wrote Mono.Unix.Native.Syscall.

The original calls from Mono.Posix.Syscall (now marked as Obsolete) all correctly use signed integers.

                [DllImport ("libc", SetLastError=true)]
                public static extern int chown (string path, int owner, int group);
                [DllImport ("libc", SetLastError=true)]
                public static extern int lchown (string path, int owner, int group);

Even the documentation directly from mcs/class/Mono.Posix/Documentation/en/Mono.Unix.Native/Syscall.xml

          <para>
            One of the owner or group id's
            may be left unchanged by specifying it as -1.
          </para>

I have changed the signatures from uint to int, the relevant XML documentation, and also 3 usages of chown within the project itself (switch from Convert.ToUInt32 to Convert.ToInt32). Hopefully this PR won't sit here for years, but who knows.

[dnfclas]

All CLA requirements met.

[akoeplinger]

@monojenkins build

[nicholi]

Can't believe I totally spaced on the return types there.

[akoeplinger]

@nicholi it does introduce an API breaking change though so I think we'll need to add an overload for the existing uint-taking public methods.

[nicholi]

@akoeplinger Semi-related, would it be posible to request a more recent build uploaded to NuGet?

https://www.nuget.org/packages/Mono.Posix.NETStandard

The last one was quite awhile ago. Though it doesn't look like too many serious changes have been committed since then. Other than this one possibly.

[nicholi]

@nicholi it does introduce an API breaking change though so I think we'll need to add an overload for the existing uint-taking public methods.

Yeah I wasn't too sure on that, since the uint versions were technically incorrect all along. Re-added them back in marked regions, and also with Obsolete attribute. That seems most appropriate correct?

[akoeplinger]

Re-added them back in marked regions, and also with Obsolete attribute. That seems most appropriate correct?

Yes that looks fine.

would it be posible to request a more recent build uploaded to NuGet?

I'll ping the relevant people after this was merged.

[akoeplinger]

@monojenkins approve

[akoeplinger]

@monojenkins commit apidiff

[akoeplinger]

@nicholi thank you for the contribution!