Remove use of include_next from c++ headers

Using include_next bypasses the default header search path and lets
files later in the include path take priority over earlier files.

This makes replacing libc impossible as the default libc headers will
occur after the libstdc++ headers, and so be picked up in place of
headers inserted at the begining of the search path or appended to the
end of the search path.

Using include_next is a hack to work-around broken combinations of
libraries, and is not necessary in a well constructed toolchain.

Signed-off-by: Keith Packard <keithp@keithp.com>

libstdc++-v3/include/bits/std_abs.h

@@ -35,9 +35,9 @@
 #include <bits/c++config.h>
 
 #define _GLIBCXX_INCLUDE_NEXT_C_HEADERS
-#include_next <stdlib.h>
+#include <stdlib.h>
 #ifdef __CORRECT_ISO_CPP_MATH_H_PROTO
-# include_next <math.h>
+# include <math.h>
 #endif
 #undef _GLIBCXX_INCLUDE_NEXT_C_HEADERS
 

libstdc++-v3/include/c/cassert

@@ -31,4 +31,4 @@
 #pragma GCC system_header
 
 #include <bits/c++config.h>
-#include_next <assert.h>
+#include <assert.h>

libstdc++-v3/include/c/cctype

@@ -31,6 +31,6 @@
 
 #pragma GCC system_header
 
-#include_next <ctype.h>
+#include <ctype.h>
 
 #endif

libstdc++-v3/include/c/cerrno

@@ -41,7 +41,7 @@
 #pragma GCC system_header
 
 #include <bits/c++config.h>
-#include_next <errno.h>
+#include <errno.h>
 
 // Adhere to section 17.4.1.2 clause 5 of ISO 14882:1998
 #ifndef errno

libstdc++-v3/include/c/cfloat

@@ -32,6 +32,6 @@
 #pragma GCC system_header
 
 #include <bits/c++config.h>
-#include_next <float.h>
+#include <float.h>
 
 #endif

libstdc++-v3/include/c/climits

@@ -32,6 +32,6 @@
 #pragma GCC system_header
 
 #include <bits/c++config.h>
-#include_next <limits.h>
+#include <limits.h>
 
 #endif

libstdc++-v3/include/c/clocale

@@ -31,6 +31,6 @@
 
 #pragma GCC system_header
 
-#include_next <locale.h>
+#include <locale.h>
 
 #endif

libstdc++-v3/include/c/cmath

@@ -33,7 +33,7 @@
 
 #include <bits/c++config.h>
 
-#include_next <math.h>
+#include <math.h>
 
 // Get rid of those macros defined in <math.h> in lieu of real functions.
 #undef abs

libstdc++-v3/include/c/csetjmp

@@ -31,7 +31,7 @@
 
 #pragma GCC system_header
 
-#include_next <setjmp.h>
+#include <setjmp.h>
 
 // Get rid of those macros defined in <setjmp.h> in lieu of real functions.
 #undef longjmp

libstdc++-v3/include/c/csignal

@@ -31,6 +31,6 @@
 
 #pragma GCC system_header
 
-#include_next <signal.h>
+#include <signal.h>
 
 #endif

libstdc++-v3/include/c/cstdarg

@@ -32,6 +32,6 @@
 #pragma GCC system_header
 
 #undef __need___va_list
-#include_next <stdarg.h>
+#include <stdarg.h>
 
 #endif

libstdc++-v3/include/c/cstddef

@@ -35,6 +35,6 @@
 #define __need_ptrdiff_t
 #define __need_NULL
 #define __need_offsetof
-#include_next <stddef.h>
+#include <stddef.h>
 
 #endif

libstdc++-v3/include/c/cstdio

@@ -31,7 +31,7 @@
 
 #pragma GCC system_header
 
-#include_next <stdio.h>
+#include <stdio.h>
 
 // Get rid of those macros defined in <stdio.h> in lieu of real functions.
 #undef clearerr

libstdc++-v3/include/c/cstdlib

@@ -31,6 +31,6 @@
 
 #pragma GCC system_header
 
-#include_next <stdlib.h>
+#include <stdlib.h>
 
 #endif

libstdc++-v3/include/c/cstring

@@ -31,6 +31,6 @@
 
 #pragma GCC system_header
 
-#include_next <string.h>
+#include <string.h>
 
 #endif

libstdc++-v3/include/c/ctime

@@ -31,6 +31,6 @@
 
 #pragma GCC system_header
 
-#include_next <time.h>
+#include <time.h>
 
 #endif

libstdc++-v3/include/c/cuchar

@@ -39,7 +39,7 @@
 #include <cwchar>
 
 #if _GLIBCXX_USE_C11_UCHAR_CXX11
-# include_next <uchar.h>
+# include <uchar.h>
 #endif
 
 #endif // C++11

libstdc++-v3/include/c/cwchar

@@ -36,7 +36,7 @@
 #include <ctime>
 
 #if _GLIBCXX_HAVE_WCHAR_H
-#include_next <wchar.h>
+#include <wchar.h>
 #endif
 
 // Need to do a bit of trickery here with mbstate_t as char_traits

libstdc++-v3/include/c/cwctype

@@ -34,7 +34,7 @@
 #include <bits/c++config.h>
 
 #if _GLIBCXX_HAVE_WCTYPE_H
-#include_next <wctype.h>
+#include <wctype.h>
 #endif
 
 #endif

libstdc++-v3/include/c_global/cmath

@@ -44,7 +44,7 @@
 #include <bits/cpp_type_traits.h>
 #include <ext/type_traits.h>
 #define _GLIBCXX_INCLUDE_NEXT_C_HEADERS
-#include_next <math.h>
+#include <math.h>
 #undef _GLIBCXX_INCLUDE_NEXT_C_HEADERS
 #include <bits/std_abs.h>
 

libstdc++-v3/include/c_global/cstdlib

@@ -76,7 +76,7 @@ namespace std
 // Need to ensure this finds the C library's <stdlib.h> not a libstdc++
 // wrapper that might already be installed later in the include search path.
 #define _GLIBCXX_INCLUDE_NEXT_C_HEADERS
-#include_next <stdlib.h>
+#include <stdlib.h>
 #undef _GLIBCXX_INCLUDE_NEXT_C_HEADERS
 #include <bits/std_abs.h>