Mark stack as not executable. Although its tempting to generate code and…

Mark stack as not executable.  Although its tempting to generate code and execute it as an optimization, security says this is a bad thing.
BUG=none
TEST=none
Review URL: https://webrtc-codereview.appspot.com/989005

git-svn-id: http://libyuv.googlecode.com/svn/trunk@518 16f28f9a-4ce2-e073-06de-1de4eb20be90

source/row_x86.asm

@@ -15,6 +15,16 @@
 %endif
 %include "x86inc.asm"
 
+%ifidn __OUTPUT_FORMAT__,elf
+section .note.GNU-stack noalloc noexec nowrite progbits
+%endif
+%ifidn __OUTPUT_FORMAT__,elf32
+section .note.GNU-stack noalloc noexec nowrite progbits
+%endif
+%ifidn __OUTPUT_FORMAT__,elf64
+section .note.GNU-stack noalloc noexec nowrite progbits
+%endif
+
 SECTION .text
 
 ; cglobal numeric constants are parameters, gpr regs, mm regs