utils.c (gnat_poplevel): Use block_chainon.

gcc/ada/
	* gcc-interface/utils.c (gnat_poplevel): Use block_chainon.

gcc/
	* function.h (block_chainon): Declare.
	* function.c (block_chainon): Define.

gcc/cp/
	* decl.c (poplevel): Use block_chainon.

gcc/fortran//
	* f95-lang.c (poplevel): Use BLOCK_CHAIN and block_chainon.

gcc/java/
	* decl.c (poplevel): Use BLOCK_CHAIN and block_chainon.

From-SVN: r172418