* changes:
Only use .text sections for aout
Use newer x86inc.asm
Use .text instead of .rodata on macho
Copy PIC handling code from x86_abi_support
Set 'private_extern' visibility for macho targets
Avoid 'amdnop' when building with nasm
Catch all elf formats
Expand PIC default to macho64 and respect CONFIG_PIC from libvpx
Use libvpx defines to set name mangling rules
Customize x86inc.asm for libvpx