Hide internal __gettextparse function [BZ #18822]

Hide internal __gettextparse function to allow direct access within
libc.so and libc.a without using GOT nor PLT.

	[BZ #18822]
	* include/plural-exp.h: New file.
	* intl/plural-exp.c: Include <plural-exp.h> instead of
	"plural-exp.h".

ChangeLog

@@ -1,3 +1,10 @@
+2017-10-01  H.J. Lu  <hongjiu.lu@intel.com>
+
+	[BZ #18822]
+	* include/plural-exp.h: New file.
+	* intl/plural-exp.c: Include <plural-exp.h> instead of
+	"plural-exp.h".
+
 2017-10-01  H.J. Lu  <hongjiu.lu@intel.com>
 
 	[BZ #18822]

include/plural-exp.h

@@ -0,0 +1,8 @@
+#ifndef _PLURAL_EXP_H
+#include <intl/plural-exp.h>
+
+#ifndef _ISOMAC
+extern __typeof (__gettextparse) __gettextparse attribute_hidden;
+#endif /* !_ISOMAC */
+
+#endif

intl/plural-exp.c

@@ -23,7 +23,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "plural-exp.h"
+#include <plural-exp.h>
 
 #if (defined __GNUC__ && !(defined __APPLE_CC_ && __APPLE_CC__ > 1) && \
      !defined __cplusplus)					       \