* gendef (fefunc): Fix incorrect pc-relative jmp instruction.
	(_sigfe): Fix offset to return address on stack.  Add and fix comments.
	(_sigbe): Fix stack alignment when creating spill area for call to
	yield.  Add and fix comments.
	(sigdelayed): Add fake push to make sure stack is aligned correctly.
	Use fake stack alignment on exit to store return address and call ret,
	rather than jmp.  Fix comments.
	(_cygtls::lock): Only create and destroy spill area when really calling
	yield.