Rename <xlocale.h> back to <sys/_locale.h>

libX11 provides <X11/Xlocale.h>.  The build of libX11 itself adds
include/X11 to the compiler's include path.  This results in a name
collision with /usr/include/xlocale.h on case-insensitive filesystems.

Commit 90e35b1eb3 renamed sys/_locale.h to xlocale.h in March 2017 under
the assumption that we should provide the locale_t type in the same file
as on Linux, FreeBSD, and Darwin.

A few weeks later (June 2017), glibc removed the xlocale.h file in favor
of bits/types/locale_t.h, which shouldn't be included directly anyway.

For reference and the reasoning, see
https://sourceware.org/git/?p=glibc.git;a=commit;h=f0be25b6336d

Given the above, revert 90e35b1eb3 and
fix additional usage of xlocale.h.

newlib/libc/include/ctype.h

@@ -5,7 +5,7 @@
 #include <sys/cdefs.h>
 
 #if __POSIX_VISIBLE >= 200809 || __MISC_VISIBLE || defined (_COMPILING_NEWLIB)
-#include <xlocale.h>
+#include <sys/_locale.h>
 #endif
 
 _BEGIN_STD_C

newlib/libc/include/inttypes.h

@@ -22,7 +22,7 @@
 #include <stddef.h>
 
 #if __BSD_VISIBLE
-#include <xlocale.h>
+#include <sys/_locale.h>
 #endif
 
 #define __STRINGIFY(a) #a

newlib/libc/include/langinfo.h

@@ -32,7 +32,7 @@
 #include <sys/cdefs.h>
 #include <sys/_types.h>
 #if __POSIX_VISIBLE >= 200809
-#include <xlocale.h>
+#include <sys/_locale.h>
 #endif
 
 #ifndef _NL_ITEM_DECLARED

newlib/libc/include/locale.h

@@ -23,7 +23,7 @@
 
 #if __POSIX_VISIBLE >= 200809 || defined (_COMPILING_NEWLIB)
 
-#include <xlocale.h>
+#include <sys/_locale.h>
 
 #define LC_ALL_MASK		(1 << LC_ALL)
 #define LC_COLLATE_MASK		(1 << LC_COLLATE)

newlib/libc/include/stdlib.h

@@ -27,7 +27,7 @@
 #endif
 
 #if __GNU_VISIBLE
-#include <xlocale.h>
+#include <sys/_locale.h>
 #endif
 
 _BEGIN_STD_C

newlib/libc/include/string.h

@@ -17,7 +17,7 @@
 #include <stddef.h>
 
 #if __POSIX_VISIBLE >= 200809
-#include <xlocale.h>
+#include <sys/_locale.h>
 #endif
 
 #if __BSD_VISIBLE

newlib/libc/include/strings.h

@@ -33,7 +33,7 @@
 #include <sys/_types.h>
 
 #if __POSIX_VISIBLE >= 200809
-#include <xlocale.h>
+#include <sys/_locale.h>
 #endif
 
 #ifndef _SIZE_T_DECLARED

newlib/libc/include/sys/_locale.h

@@ -1,7 +1,7 @@
 /* Definition of opaque POSIX-1.2008 type locale_t for userspace. */
 
-#ifndef	_XLOCALE_H
-#define _XLOCALE_H
+#ifndef	_SYS__LOCALE_H
+#define _SYS__LOCALE_H
 
 #include <newlib.h>
 #include <sys/config.h>
@@ -9,4 +9,4 @@
 struct __locale_t;
 typedef struct __locale_t *locale_t;
 
-#endif	/* _XLOCALE_H */
+#endif	/* _SYS__LOCALE_H */

newlib/libc/include/time.h

@@ -29,7 +29,7 @@
 #include <sys/timespec.h>
 
 #if __POSIX_VISIBLE >= 200809
-#include <xlocale.h>
+#include <sys/_locale.h>
 #endif
 
 _BEGIN_STD_C

newlib/libc/include/wchar.h

@@ -64,7 +64,7 @@ typedef __gnuc_va_list va_list;
 #endif
 
 #if __POSIX_VISIBLE >= 200809
-#include <xlocale.h>
+#include <sys/_locale.h>
 #endif
 
 _BEGIN_STD_C

newlib/libc/include/wctype.h

@@ -8,7 +8,7 @@
 #include <stddef.h>
 
 #if __POSIX_VISIBLE >= 200809
-#include <xlocale.h>
+#include <sys/_locale.h>
 #endif
 
 #ifndef WEOF

winsup/cygwin/include/monetary.h

@@ -32,7 +32,7 @@
 #include <sys/cdefs.h>
 #include <sys/types.h>
 #if __POSIX_VISIBLE >= 200809
-#include <xlocale.h>
+#include <sys/_locale.h>
 #endif
 
 __BEGIN_DECLS

winsup/cygwin/release/3.1.0

@@ -16,6 +16,9 @@ What changed:
 - If a SA_SIGINFO signal handler changes the ucontext_t pointed to by
   the third parameter, follow it after returning from the handler.
 
+- Eliminate a header file name collision with <X11/XLocale.h> on case
+  insensitive filesystems by reverting <xlocale.h> back to <sys/_locale.h>.
+
 
 Bug Fixes
 ---------

winsup/doc/new-features.xml

@@ -8,6 +8,12 @@
 
 <itemizedlist mark="bullet">
 
+<listitem><para>
+Eliminate a header file name collision with &lt;X11/XLocale.h&gt; on
+case insensitive filesystems by reverting &lt;xlocale.h&gt; back to
+&lt;sys/_locale.h&gt;.
+</para></listitem>
+
 <listitem><para>
 FIFOs can now be opened multiple times for writing.
 </para></listitem>