Restore build with GCC 4.8 to GCC 5

Restore build with GCC 4.8 to GCC 5

GCC 5 and earlier applied array-to-pointer decay too early,
which affected the new attribute namespace code.  A reduced
example of the construct that the attribute code uses is:

    struct S { template<__SIZE_TYPE__ N> S(int (&)[N]); };
    struct T { int a; S b; };
    int a[] = { 1 };
    T t = { 1, a };

This was fixed by f85e1317f8ea933f5c615680353bd646f480f7d3
(PR 16333 et al).

This patch tries to add a minimally-invasive workaround.

gcc/ada/
	* gcc-interface/utils.cc (gnat_internal_attribute_table): Add extra
	braces to work around PR 16333 in older compilers.

gcc/
	* attribs.cc (handle_ignored_attributes_option): Add extra
	braces to work around PR 16333 in older compilers.
	* config/aarch64/aarch64.cc (aarch64_gnu_attribute_table): Likewise.
	(aarch64_arm_attribute_table): Likewise.
	* config/arm/arm.cc (arm_gnu_attribute_table): Likewise.
	* config/i386/i386-options.cc (ix86_gnu_attribute_table): Likewise.
	* config/ia64/ia64.cc (ia64_gnu_attribute_table): Likewise.
	* config/rs6000/rs6000.cc (rs6000_gnu_attribute_table): Likewise.
	* target-def.h (TARGET_GNU_ATTRIBUTES): Likewise.
	* genhooks.cc (emit_init_macros): Likewise, when emitting the
	instantiation of TARGET_ATTRIBUTE_TABLE.
	* langhooks-def.h (LANG_HOOKS_INITIALIZER): Likewise, when
	instantiating LANG_HOOKS_ATTRIBUTE_TABLE.
	(LANG_HOOKS_ATTRIBUTE_TABLE): Define to be empty by default.
	* target.def (attribute_table): Likewise.

gcc/c-family/
	* c-attribs.cc (c_common_gnu_attribute_table): Add extra
	braces to work around PR 16333 in older compilers.

gcc/c/
	* c-decl.cc (std_attribute_table): Add extra braces to work
	around PR 16333 in older compilers.

gcc/cp/
	* tree.cc (cxx_gnu_attribute_table): Add extra braces to work
	around PR 16333 in older compilers.

gcc/d/
	* d-attribs.cc (d_langhook_common_attribute_table): Add extra braces
	to work around PR 16333 in older compilers.
	(d_langhook_gnu_attribute_table): Likewise.

gcc/fortran/
	* f95-lang.cc (gfc_gnu_attribute_table): Add extra braces to work
	around PR 16333 in older compilers.

gcc/jit/
	* dummy-frontend.cc (jit_gnu_attribute_table): Add extra braces
	to work around PR 16333 in older compilers.
	(jit_format_attribute_table): Likewise.

gcc/lto/
	* lto-lang.cc (lto_gnu_attribute_table): Add extra braces to work
	around PR 16333 in older compilers.
	(lto_format_attribute_table): Likewise.