Defect in XSH pthread_attr_getguardsize

[yyyyyyyy@xxxxxxx]

        Defect report from : Loic Domaigne , Personal Interest

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@ page 986 line 31459 section pthread_attr_getguardsize objection 
{pthread_attr_getguardsize}

Problem:

Edition of Specification (Year): 2003

Defect code :  1. Error

Reference are given against TC1.

They are inconsistencies in the errors handling between the 
pthread_attr_* XSH.

For pthread_attr_{get|set}guardsize(), the standard specifies a 
"shall fail" for the validation of attr. As explained by David 
Butenhof on austin-group-l:

| Generally, no validation of attr should be "shall fail", because it's 
| impractical (if not impossible) to provide a real guarantee that an 
| attributes object is uncorrupted and in every respect "valid"

We suggest to weaken the "shall fail" by a "may fail". 

Action:

- Remove line 31461.

- Add: 

The pthread_attr_getguardsize() and pthread_attr_setguardsize may fail 
if:
[EINVAL] 
The value specified by attr does not refer to an initialized
thread attribute object.