libunwind: initial version 1.1

The package Makefile was based on work at link [1] with the following
changes

1. Disable minidebuginfo support thus no dependency on liblzma
2. Add 2 patches for building against musl-libc and building with
mips16 enabled
3. Add LICENSE and DEPENDS info, etc.

[1] https://github.com/rpi-openwrt/rpi-packages/tree/master/libs/libunwind

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>