vpxdec: Rename the libyuv scale wrapper.

The other name was misleading: We do not export scaling support from
libvpx via vpx_im{g,age}*.

Change-Id: I8acb4ea0301f08c9bab557a4063ea35d147b4631
iosbuild.sh: Add targets argument.

Allows override of default target list. Also added missing usage info
for --extra-configure-args, and removed last vestiges of armv6 support.

Change-Id: Ic0f14fffa0cbaea1bed371d38ff65e035bbe3273
Optimize bit_read_buffer.

Change-Id: Iee43c34909deec9787b29c1c33672213b9f049df
Merge "iosbuild.sh: Add targets argument."
Merge "vpxdec: Rename the libyuv scale wrapper."
Merge "Optimize bit_read_buffer."