Move <sys/_sigdefs.h> and <sys/_errdefs.h> to private.

Bug: http://b/28067717
Change-Id: I02f78ad7293a15ff45e35e9c20f60d3d023931eb
diff --git a/libc/bionic/strerror_r.cpp b/libc/bionic/strerror_r.cpp
index d419fb1..a0a0809 100644
--- a/libc/bionic/strerror_r.cpp
+++ b/libc/bionic/strerror_r.cpp
@@ -31,7 +31,7 @@
 
 static const Pair _sys_error_strings[] = {
 #define  __BIONIC_ERRDEF(x,y,z)  { x, z },
-#include <sys/_errdefs.h>
+#include "private/bionic_errdefs.h"
   { 0, NULL }
 };
 
@@ -41,7 +41,7 @@
 
 static const Pair _sys_signal_strings[] = {
 #define  __BIONIC_SIGDEF(signal_number, signal_description)  { signal_number, signal_description },
-#include <sys/_sigdefs.h>
+#include "private/bionic_sigdefs.h"
   { 0, NULL }
 };
 
diff --git a/libc/bionic/sys_siglist.c b/libc/bionic/sys_siglist.c
index 3cfddbf..8e33d64 100644
--- a/libc/bionic/sys_siglist.c
+++ b/libc/bionic/sys_siglist.c
@@ -30,5 +30,5 @@
 
 const char* const sys_siglist[NSIG] = {
 #define __BIONIC_SIGDEF(signal_number, signal_description) [ signal_number ] = signal_description,
-#include <sys/_sigdefs.h>
+#include "private/bionic_sigdefs.h"
 };
diff --git a/libc/bionic/sys_signame.c b/libc/bionic/sys_signame.c
index e1286f2..5158b83 100644
--- a/libc/bionic/sys_signame.c
+++ b/libc/bionic/sys_signame.c
@@ -30,5 +30,5 @@
 
 const char* const sys_signame[NSIG] = {
 #define __BIONIC_SIGDEF(signal_number, unused) [ signal_number ] = #signal_number + 3,
-#include <sys/_sigdefs.h>
+#include "private/bionic_sigdefs.h"
 };
diff --git a/libc/include/sys/_errdefs.h b/libc/private/bionic_errdefs.h
similarity index 100%
rename from libc/include/sys/_errdefs.h
rename to libc/private/bionic_errdefs.h
diff --git a/libc/include/sys/_sigdefs.h b/libc/private/bionic_sigdefs.h
similarity index 100%
rename from libc/include/sys/_sigdefs.h
rename to libc/private/bionic_sigdefs.h