Remove bare use of __attribute__ in include/errno.h.

This is just a style fix; we always prefer the shorthand macros over
bare uses of __attribute__, even in private headers.

	* include/errno.h (__errno_location): Use __attribute_const__
	instead of bare __attribute__.

ChangeLog

@@ -1,3 +1,8 @@
+2017-06-09  Zack Weinberg  <zackw@panix.com>
+
+	* include/errno.h (__errno_location): Use __attribute_const__
+	instead of bare __attribute__.
+
 2017-06-09  Zack Weinberg  <zackw@panix.com>
 
 	* Makeconfig (dl-tunable-list.h): Generate using a stamp file.

include/errno.h

@@ -39,7 +39,7 @@ extern __thread int errno attribute_tls_model_ie;
 # define __set_errno(val) (errno = (val))
 
 # ifndef __ASSEMBLER__
-extern int *__errno_location (void) __THROW __attribute__ ((__const__))
+extern int *__errno_location (void) __THROW __attribute_const__
 #  if RTLD_PRIVATE_ERRNO
      attribute_hidden
 #  endif