internal/stdbool.h rework

Noticed that internal/stdbool.h and addr2line.c are the only two place
where missing/stdbool.h is included.  Why not delete the file so that
we can merge internal/stdbool.h and missing/stdbool.h into one.

addr2line.c

@@ -25,11 +25,7 @@
 #include <libproc.h>
 #endif
 
-#ifdef HAVE_STDBOOL_H
-#include <stdbool.h>
-#else
-#include "missing/stdbool.h"
-#endif
+#include "internal/stdbool.h"
 
 #if defined(USE_ELF) || defined(HAVE_MACH_O_LOADER_H)
 

internal/stdbool.h

@@ -13,8 +13,22 @@
 
 #ifdef HAVE_STDBOOL_H
 # include <stdbool.h>
-#else
-# include "missing/stdbool.h"
 #endif
 
+/* Note that we assume the compiler isn't C++. */
+#ifdef __bool_true_false_are_defined
+# undef bool
+# undef true
+# undef false
+# undef __bool_true_false_are_defined
+#else
+typedef unsigned char _Bool;
+#endif
+
+/* See also http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2229.htm */
+#define bool  _Bool
+#define true  ((_Bool)+1)
+#define false ((_Bool)+0)
+#define __bool_true_false_are_defined
+
 #endif /* INTERNAL_STDBOOL_H */

missing/stdbool.h

@@ -1,20 +0,0 @@
-/*
- * missing/stdbool.h: Quick alternative of C99 stdbool.h
- */
-
-#ifndef _MISSING_STDBOOL_H_
-#define _MISSING_STDBOOL_H_
-
-#ifndef __bool_true_false_are_defined
-# ifndef __cplusplus
-#  undef bool
-#  undef false
-#  undef true
-#  define bool signed char
-#  define false 0
-#  define true 1
-#  define __bool_true_false_are_defined 1
-# endif
-#endif
-
-#endif /* _MISSING_STDBOOL_H_ */