Only warn for unknown options in configure script
Only warn for unknown options in configure script

This follows discussion started at
http://lists.nongnu.org/archive/html/tinycc-devel/2012-05/msg00015.html

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