Byte-swapping issue in getresuid on qemu-user-sparc64
Description of problem:
When calling getresuid() in the big-endian sparc64 guest, the uid_t values are written with their 16-bit halves reversed.

For example, the UID 0x000003e8 (1000) becomes 0x03e80000.
Steps to reproduce:
A minimal test case looks like this:
```c
#define _GNU_SOURCE
#include <stdio.h>
#include <sys/types.h>
#include <pwd.h>
#include <unistd.h>

int main(int argc, char **argv) {
	struct passwd *pw = getpwuid(geteuid());
	if (pw == NULL) {
		perror("getpwuid failure");
		return 1;
	}
	printf("getpwuid()->pw_uid=0x%08x\n", pw->pw_uid);

	uid_t ruid = 0, euid = 0, suid = 0;
	if (getresuid(&ruid, &euid, &suid) != 0) {
		perror("getresuid failure");
		return 1;
	}
	printf("getresuid()->suid=0x%08x\n", suid);

	return 0;
}
```

Compile and run with:
```
$ sparc64-linux-gnu-gcc -Wall -O0 -g -o sid-sparc64/test test.c
$ sudo chroot sid-sparc64
[chroot] $ qemu-sparc64-static ./test
```

Alternatively, static compilation without a chroot is also possible (despite a warning about `getpwuid()`):
```
$ sparc64-linux-gnu-gcc -static -Wall -O0 -g -o test test.c
$ qemu-sparc64-static ./test
```

Expected output:
```
$ ./test 
getpwuid()->pw_uid=0x000003e8
getresuid()->suid=0x000003e8
```

Actual output:
```
$ ./test 
getpwuid()->pw_uid=0x000003e8
getresuid()->suid=0x03e80000
```
Additional information:
I'm not sure if this is a glibc, qemu or kernel issue, but it doesn't occur outside qemu.