Updated some links which are not working with new links

Hi,

There are some links referred in the source files which are currently
not working.

The below link:
<http://www.UNIX-systems.org/online.html>
is updated with:
<http://www.unix.org/online.html>

The below links:

http://www-01.ibm.com/support/knowledgecenter/SSGH2K_11.1.0/com.ibm.xlc111.aix.doc/language_ref/function_attributes.html
http://www-01.ibm.com/support/knowledgecenter/SSGH2K_11.1.0/com.ibm.xlc111.aix.doc/language_ref/type_attrib.html
are updated with:

http://www-01.ibm.com/support/knowledgecenter/SSGH2K_13.1.2/com.ibm.xlc131.aix.doc/language_ref/function_attributes.html
http://www-01.ibm.com/support/knowledgecenter/SSGH2K_13.1.2/com.ibm.xlc131.aix.doc/language_ref/type_attrib.html

In c.h the link was not updated but in generic-xlc.h the link has been
updated earlier.

Attached patch contains the fix with the updated links.

Regards,
Vignesh
EnterpriseDB: http://www.enterprisedb.com