libvpx

Merge changes from topic 'x86inc'

* 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