x86_64: Implement GET_CALLER_FP
x86_64: Implement GET_CALLER_FP

TCC always uses %rbp frames, so we can use that one.

gfwilliams/tinycc,FriedBreakfast/tcc,run4flat/tinycc,gfwilliams/tinycc,metaeducation/tcc,acook/tinycc,soywiz/tinycc,avih/tinycc,fstudio/tinycc,rchandramouli/tinycc,leeduhem/tinycc,gfwilliams/tinycc,andrewchambers/tccmirror,andrewchambers/tccmirror,seyko2/tinycc,ftdi-paul-jiao/tinyCC,run4flat/tinycc,mobiphil/tinnycc,mitake/tinycc,soywiz/tinycc,mitake/tinycc,Saectar/inherpreter,mobiphil/tinnycc,melkior/tinycc,andreiw/tinycc,mobiphil/tinnycc,rchandramouli/tinycc,fstudio/tinycc,Saectar/inherpreter,Saectar/inherpreter,andrewchambers/tccmirror,rchandramouli/tinycc,avih/tinycc,yousong/tinycc,code4game/tinycc,run4flat/tinycc,melkior/tinycc,Archs/TinyCC,andrewchambers/tccmirror,mingodad/tinycc,mingodad/tinycc,FriedBreakfast/tcc,run4flat/tinycc,FriedBreakfast/tcc,andreiw/tinycc,yousong/tinycc,gfwilliams/tinycc,run4flat/tinycc,ftdi-paul-jiao/tinyCC,Archs/TinyCC,mirror/tinycc,leeduhem/tinycc,FriedBreakfast/tcc,rchandramouli/tinycc,mirror/tinycc,yousong/tinycc,fstudio/tinycc,fstudio/tinycc,melkior/tinycc,Saectar/inherpreter,metaeducation/tcc,rchandramouli/tinycc,code4game/tinycc,leeduhem/tinycc,mingodad/tinycc,leeduhem/tinycc,ftdi-paul-jiao/tinyCC,mirror/tinycc,Saectar/inherpreter,metaeducation/tcc,avih/tinycc,acook/tinycc,fstudio/tinycc,seyko2/tinycc,gfwilliams/tinycc,yousong/tinycc,seyko2/tinycc,ftdi-paul-jiao/tinyCC,Archs/TinyCC,metaeducation/tcc,alfonsokim/tinycc,acook/tinycc,soywiz/tinycc,andreiw/tinycc,code4game/tinycc,Archs/TinyCC,mobiphil/tinnycc,FriedBreakfast/tcc,mirror/tinycc,seyko2/tinycc,seyko2/tinycc,alfonsokim/tinycc,leeduhem/tinycc,soywiz/tinycc,mingodad/tinycc,Archs/TinyCC,melkior/tinycc,mitake/tinycc,avih/tinycc,melkior/tinycc,metaeducation/tcc,andrewchambers/tccmirror,alfonsokim/tinycc,alfonsokim/tinycc,mitake/tinycc,acook/tinycc,alfonsokim/tinycc