Import libiberty from gcc

PR 29200
include/
	* ansidecl.h,
	* demangle.h: Import from gcc.
libiberty/
	* cp-demangle.c,
	* testsuite/demangle-expected: Import from gcc.

include/ansidecl.h

@@ -321,47 +321,6 @@ So instead we use the macro below and test it against specific values.  */
 #define CONSTEXPR
 #endif
 
-/* C++11 adds the ability to add "override" after an implementation of a
-   virtual function in a subclass, to:
-     (A) document that this is an override of a virtual function
-     (B) allow the compiler to issue a warning if it isn't (e.g. a mismatch
-         of the type signature).
-
-   Similarly, it allows us to add a "final" to indicate that no subclass
-   may subsequently override the vfunc.
-
-   Provide OVERRIDE and FINAL as macros, allowing us to get these benefits
-   when compiling with C++11 support, but without requiring C++11.
-
-   For gcc, use "-std=c++11" to enable C++11 support; gcc 6 onwards enables
-   this by default (actually GNU++14).  */
-
-#if defined __cplusplus
-# if __cplusplus >= 201103
-   /* C++11 claims to be available: use it.  Final/override were only
-      implemented in 4.7, though.  */
-#  if GCC_VERSION < 4007
-#   define OVERRIDE
-#   define FINAL
-#  else
-#   define OVERRIDE override
-#   define FINAL final
-#  endif
-# elif GCC_VERSION >= 4007
-   /* G++ 4.7 supports __final in C++98.  */
-#  define OVERRIDE
-#  define FINAL __final
-# else
-   /* No C++11 support; leave the macros empty.  */
-#  define OVERRIDE
-#  define FINAL
-# endif
-#else
-  /* No C++11 support; leave the macros empty.  */
-# define OVERRIDE
-# define FINAL
-#endif
-
 /* A macro to disable the copy constructor and assignment operator.
    When building with C++11 and above, the methods are explicitly
    deleted, causing a compile-time error if something tries to copy.

include/demangle.h

@@ -449,7 +449,14 @@ enum demangle_component_type
   /* A cloned function.  */
   DEMANGLE_COMPONENT_CLONE,
   DEMANGLE_COMPONENT_NOEXCEPT,
-  DEMANGLE_COMPONENT_THROW_SPEC
+  DEMANGLE_COMPONENT_THROW_SPEC,
+
+  DEMANGLE_COMPONENT_STRUCTURED_BINDING,
+
+  DEMANGLE_COMPONENT_MODULE_NAME,
+  DEMANGLE_COMPONENT_MODULE_PARTITION,
+  DEMANGLE_COMPONENT_MODULE_ENTITY,
+  DEMANGLE_COMPONENT_MODULE_INIT,
 };
 
 /* Types which are only used internally.  */