6g: simplify trampoline by postponing load.
6g: simplify trampoline by postponing load.

	TEXT tramp
		MOVQ 8(SP), AX
		ADDQ $40, AX
		MOVQ AX, 8(SP)
		JMP oldfunc

	is now

	TEXT tramp
		ADDQ $40, 8(SP)
		JMP oldfunc

	and if s/40/0/, then it simplifies to

	TEXT tramp
		JMP oldfunc

	(the tramp is still needed to satisfy
	symbol references from other object files)

R=ken
OCL=28377
CL=28381

rdp/rogerpack2005-golang,mhennings/marcohennings-go,mhennings/marcohennings-go,npe9/noahevans-go9,webfd/go-zh,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,Triskite/willstone-goclone,rdp/rogerpack2005-golang,bryanxu/go-zh,npe9/noahevans-go9,glycerine/jeaten-go-arrayof-structof,mhennings/marcohennings-go,d0f/go-zh,d0f/go-zh,npe9/noahevans-go9,npe9/noahevans-go9,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,rflanagan/reginaldflanagan-project1,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,npe9/noahevans-go9,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,Triskite/willstone-goclone,webfd/go-zh,rflanagan/reginaldflanagan-project1,sanjosh/sanjos100-tipc,npe9/noahevans-go9,rflanagan/reginaldflanagan-project1,rdp/rogerpack2005-golang,Triskite/willstone-goclone,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,bryanxu/go-zh,Triskite/willstone-goclone,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,rflanagan/reginaldflanagan-project1,webfd/go-zh,mhennings/marcohennings-go,glycerine/jeaten-go-arrayof-structof,rflanagan/reginaldflanagan-project1,npe9/noahevans-go9,scirelli/scirelli-go,scirelli/scirelli-go,rdp/rogerpack2005-golang,scirelli/scirelli-go,d0f/go-zh,webfd/go-zh,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,scirelli/scirelli-go,scirelli/scirelli-go,Triskite/willstone-goclone,mhennings/marcohennings-go,rdp/rogerpack2005-golang,Triskite/willstone-goclone,rdp/rogerpack2005-golang,scirelli/scirelli-go,Triskite/willstone-goclone,d0f/go-zh,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,bryanxu/go-zh,Triskite/willstone-goclone,mhennings/marcohennings-go,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,bryanxu/go-zh,d0f/go-zh,rflanagan/reginaldflanagan-project1,webfd/go-zh,webfd/go-zh,d0f/go-zh,webfd/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,npe9/noahevans-go9,webfd/go-zh,scirelli/scirelli-go