d: Fix the build on hosts missing _MAX and _MAX macros.

gcc/d/ChangeLog:

2019-04-17  Iain Buclaw  <ibuclaw@gdcproject.org>

	* d-system.h (POSIX): Define unix as POSIX.
	(INT32_MAX, INT32_MIN, INT64_MIN, UINT32_MAX, UINT64_MAX): Provide
	fallback definitions.

From-SVN: r270403

gcc/d/ChangeLog

+2019-04-17  Iain Buclaw  <ibuclaw@gdcproject.org>
+
+	* d-system.h (POSIX): Define unix as POSIX.
+	(INT32_MAX, INT32_MIN, INT64_MIN, UINT32_MAX, UINT64_MAX): Provide
+	fallback definitions.
+
 2019-04-16  Iain Buclaw  <ibuclaw@gdcproject.org>
 
 	* Make-lang.in (d.mostyclean): Clean idgen and impcvgen.

gcc/d/d-system.h

@@ -25,7 +25,7 @@
 /* Used by the dmd front-end to determine if we have POSIX-style IO.  */
 #define POSIX (__linux__ || __GLIBC__ || __gnu_hurd__ || __APPLE__ \
 	       || __FreeBSD__ || __NetBSD__ || __OpenBSD__ || __DragonFly__ \
-	       || __sun)
+	       || __sun || __unix__)
 
 /* Forward assert invariants to gcc_assert.  */
 #undef assert
@@ -61,4 +61,21 @@
 #define _mkdir(p) mkdir(p, 0)
 #endif
 
+/* Define any missing _MAX and _MIN macros.  */
+#ifndef INT32_MAX
+# define INT32_MAX INTTYPE_MAXIMUM (int32_t)
+#endif
+#ifndef INT32_MIN
+# define INT32_MIN INTTYPE_MINIMUM (int32_t)
+#endif
+#ifndef INT64_MIN
+# define INT64_MIN INTTYPE_MINIMUM (int64_t)
+#endif
+#ifndef UINT32_MAX
+# define UINT32_MAX INTTYPE_MAXIMUM (uint32_t)
+#endif
+#ifndef UINT64_MAX
+# define UINT64_MAX INTTYPE_MAXIMUM (uint64_t)
+#endif
+
 #endif  /* GCC_D_SYSTEM_H  */