endian.h: Define uint{16,32,64}_t

The Draft Posix Issue 8 standard requires that these be defined. Define
them in the usual way that lets multiple headers define them. Opted to
not just use #include <stdint.h>, allowed by the draft, to be
conservative. Add notes about how we comply with Issue 8, and that we've
opted to define these only as macros, though the standard allows
functions, macros or both.

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include/endian.h

@@ -11,9 +11,33 @@
 #ifndef _ENDIAN_H_
 #define _ENDIAN_H_
 
+/*
+ * POSIX Issue 8 requires that endian.h define uint{16,32,64}_t. Although POSIX
+ * allows stdint.h symbols here, be conservative and only define there required
+ * ones. FreeBSD's sys/_endian.h doesn't need to expose those types since it
+ * implements all the [bl]eXtoh hto[bl]eX interfaces as macros calling builtin
+ * functions. POSIX allows functions, macros or both. We opt for macros only.
+ */
+#include <sys/_types.h>
+
+#ifndef _UINT16_T_DECLARED
+typedef	__uint16_t		uint16_t;
+#define	_UINT16_T_DECLARED
+#endif
+
+#ifndef _UINT32_T_DECLARED
+typedef	__uint32_t		uint32_t;
+#define	_UINT32_T_DECLARED
+#endif
+
+#ifndef _UINT64_T_DECLARED
+typedef	__uint64_t		uint64_t;
+#define	_UINT64_T_DECLARED
+#endif
+
 /*
  * FreeBSD's sys/_endian.h is very close to the interface provided on Linux by
- * glibc's endian.h.
+ * glibc's endian.h as well as POSIX Issue 8's endian.h.
  */
 #include <sys/_endian.h>
 

sys/sys/_endian.h

@@ -69,8 +69,10 @@
 
 /*
  * POSIX Issue 8 will require these for endian.h. Define them there and in the
- * traditional BSD compilation environment. Since issue 8 doesn't yet have an
+ * traditional BSD compilation environment. PDP_ENDIAN isn't strictly in Issue
- * assigned date, use strictly greater than issue 7's date.
+ * 8, but is allowed as implementations can define any *_ENDIAN symbol. Since
+ * issue 8 doesn't yet have an assigned date, use strictly greater than issue
+ * 7's date.
  */
 #if __BSD_VISIBLE || _POSIX_C_SOURCE > 200809
 #define	LITTLE_ENDIAN   _LITTLE_ENDIAN