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>

package/libs/libunwind/patches/002-fix-building-getcontext_S.patch

@@ -0,0 +1,19 @@
+diff -uprN a/src/mips/getcontext.S b/src/mips/getcontext.S
+--- a/src/mips/getcontext.S	2012-10-06 12:54:38.000000000 +0800
++++ b/src/mips/getcontext.S	2016-06-08 13:35:25.033051679 +0800
+@@ -24,12 +24,12 @@ OF CONTRACT, TORT OR OTHERWISE, ARISING
+ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
+ 
+ #include "offsets.h"
+-#include <endian.h>
+ 
+ 	.text
++	.set nomips16
+ 
+ #if _MIPS_SIM == _ABIO32
+-# if __BYTE_ORDER == __BIG_ENDIAN
++# if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+ #  define OFFSET 4
+ # else
+ #  define OFFSET 0
+