unpackbootimg: stash EFIDroid changes

Source: https://github.com/efidroid/build/commits/5a8c5e9fe25cb4e0e182f55c1dc96d49a95b341c/tools/unpackbootimg

commit c0bb55fdf63c6ba5b8f4b30303ab624e5cd1eab0
Author: M1cha <sigmaepsilon92@gmail.com>
Date:   Fri Aug 26 11:12:28 2016 +0200

    unpackbootimg: extract appended fdt too

commit 39fa4df2e200501400a7f80097543c684c91ad8b
Author: M1cha <sigmaepsilon92@gmail.com>
Date:   Sun Aug 28 20:49:00 2016 +0200

    tools: unpackbootimg: don't write os_version and os_patch_level if they are 0

commit 4bf90a6ecc2530c3eb6d97d90a595655f5c8189f
Author: M1cha <sigmaepsilon92@gmail.com>
Date:   Sun Sep 4 10:54:43 2016 +0200

    tools: unpackbootimg: create output directory if it doesn't exist

commit 863757ec8f008f189aeb188a6fb8bf8718c040e6
Author: M1cha <sigmaepsilon92@gmail.com>
Date:   Sun Sep 4 10:57:02 2016 +0200

    tools: unpackbootimg: don't try to split zImage if it's too small

commit 21c7d91fce55bf6ec242ad81768f679a461166cf
Author: M1cha <sigmaepsilon92@gmail.com>
Date:   Sun Sep 4 10:57:29 2016 +0200

    tools: unpackbootimg: fix base and offset calculations

commit 5a8c5e9fe25cb4e0e182f55c1dc96d49a95b341c
Author: M1cha <sigmaepsilon92@gmail.com>
Date:   Sun Sep 4 11:09:47 2016 +0200

    tools: unpackbootimg: improve base calculation by substracting 0x8000

Change-Id: I62f4f92c5caaed06cd3858900135231f91f6bc79