Fix search.h namespace (bug 17996).

Fix search.h namespace (bug 17996).

The implementation of the (XSI POSIX) functions hsearch / hcreate /
hdestroy uses hsearch_r / hcreate_r / hdestroy_r, which are not POSIX
functions.  This patch makes those into weak aliases for __*_r and
uses those names for the calls within libc.

Tested for x86_64 that the disassembly of installed shared libraries
is unchanged by this patch.

	[BZ #17996]
	* include/search.h (hcreate_r): Don't use libc_hidden_proto.
	(hdestroy_r): Likewise.
	(hsearch_r): Likewise.
	(__hcreate_r): Declare and use libc_hidden_proto.
	(__hdestroy_r): Likewise.
	(__hsearch_r): Likewise.
	* misc/hsearch.c (hsearch): Call __hsearch_r instead of hsearch_r.
	(hcreate): Call __hcreate_r instead of hcreate_r.
	(__hdestroy): Call __hdestroy_r instead of hdestroy_r.
	* misc/hsearch_r.c (hcreate_r): Rename to __hcreate_r and define
	as weak alias of __hcreate_r.
	(hdestroy_r): Rename to __hdestroy_r and define as weak alias of
	__hdestroy_r.
	(hsearch_r): Rename to __hsearch_r and define as weak alias of
	__hsearch_r.
	* conform/Makefile (test-xfail-XPG3/search.h/linknamespace):
	Remove variable.
	(test-xfail-XPG4/search.h/linknamespace): Likewise.
	(test-xfail-UNIX98/search.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/search.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/search.h/linknamespace): Likewise.