Fix pthread_t on Macos.

From some testing with directly using C code, pthread_t on macos is 8 bytes.
This is my test code:

```
#include <assert.h>
#include <stdio.h>

#include <pthread.h>



void* PosixThreadMainRoutine(void* data)

{

	// Do some work here.
	for (int i = 0; i < 2000000000; i++) {

	}



	return NULL;

}



pthread_t LaunchThread()

{

	// Create the thread using POSIX routines.

	pthread_attr_t  attr;

	pthread_t       posixThreadID;

	int             returnVal;



	returnVal = pthread_attr_init(&attr);

	assert(!returnVal);

	returnVal = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

	assert(!returnVal);



	int     threadError = pthread_create(&posixThreadID, &attr, &PosixThreadMainRoutine, NULL);



	returnVal = pthread_attr_destroy(&attr);

	assert(!returnVal);

	if (threadError != 0)

	{

		// Report an error.

	}

	return posixThreadID;

}

int main() {
	pthread_t t = LaunchThread();

	void ** ret;


	printf("%d, %d\n", sizeof(t), sizeof(pthread_t));

	int val = pthread_join(t, ret);


	printf("%d", val);
	return 0;
}
```
running this on macos reports `8, 8`. 
Then I made the proposed changes and errors I was having with threads completely went away.

0 files changed, 0 insertions, 0 deletions