Do not declare grantpt, ptsname, unlockpt in stdlib.h for XPG3 (bug 20094).
stdlib.h declares grantpt, ptsname, unlockpt for __USE_XOPEN. This
patch corrects the condition to __USE_XOPEN_EXTENDED (these functions
are new in XPG4).
Tested for x86_64 and x86 (testsuite, and that installed shared
libraries are unchanged by the patch).
[BZ #20094]
* stdlib/stdlib.h (grantpt): Declare if [__USE_XOPEN_EXTENDED],
not [__USE_XOPEN].
(unlockpt): Likewise.
(ptsname): Likewise.
* conform/Makefile (test-xfail-XPG3/stdlib.h/conform): Remove
variable.