package/squashfs: fix host compile multiple definitions

Add upstream patch to fix squashfs-tools build failures because
of missing external declaration for fwriter_buffer and
bwriter_buffer.

Fixes:

  - http://autobuild.buildroot.net/results/6789b668898245926e0a3a3e7caf823dff515d71



  /usr/bin/ld: read_fs.o:(.bss+0x0): multiple definition of `fwriter_buffer'; mksquashfs.o:(.bss+0x400c90): first defined here
  /usr/bin/ld: read_fs.o:(.bss+0x8): multiple definition of `bwriter_buffer'; mksquashfs.o:(.bss+0x400c98): first defined here

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>