gcc:
	* cpphash.h: Remove conditional #define of __extension__.
	* rtl.h: Add __extension__ to RTL_CHECK1, RTL_CHECK2,
	RTL_CHECKC1, RTL_CHECKC2, and RTVEC_ELT macros
	(ENABLE_RTL_CHECKING only).
	* tree.h: Add __extension__ to TREE_CHECK, TREE_CLASS_CHECK,
	CST_OR_CONSTRUCTOR_CHECK, and EXPR_CHECK macros
	(ENABLE_TREE_CHECKING only).
	* varray.h: Add __extension__ to VARRAY_CHECK macro
	(ENABLE_CHECKING only).

include:
	* ansidecl.h: #define __extension__ to nothing if
	GCC_VERSION < 2008.

From-SVN: r33733