Turn RETURN_ADDR_IN_PREVIOUS_FRAME into C expression

Turn RETURN_ADDR_IN_PREVIOUS_FRAME into C expression

This allows a target to support both windowed and non-windowed ABI.

2015-03-03  Max Filippov  <jcmvbkbc@gmail.com>

gcc/
	* builtins.c (expand_builtin_return_addr): Add
	RETURN_ADDR_IN_PREVIOUS_FRAME to 'if' condition, remove
	surrounding #ifdef.
	* config/sparc/sparc.h (RETURN_ADDR_IN_PREVIOUS_FRAME): Change
	definition to 1.
	* config/xtensa/xtensa.h (RETURN_ADDR_IN_PREVIOUS_FRAME):
	Likewise.
	* defaults.h (RETURN_ADDR_IN_PREVIOUS_FRAME): Define to 0 if
	undefined.
	* doc/tm.texi.in (RETURN_ADDR_IN_PREVIOUS_FRAME): Update
	paragraph.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@221150 138bc75d-0d04-0410-961f-82ee72b054a4