init: create symlinks to mtd block device nodes

Given a device in the form of "/devices/virtual/mtd/mtd0/mtdblock0":
* Creates symlinks for mtd block devices in
  /dev/block/mtd/mtd<partition number>
* Creates symlinks based on partition name in
  /dev/block/mtd/by-name/<partition name>

Change-Id: Id8d61be88935a0ef83297d1d5e453d8ba0d586de
fastboot: Add missing fastboot USB IDs

Change-Id: I1616e9e6a57652aa919f979833c0e19479343966
libcutils: Do not use the kernel headers

No idea why this is here, but it breaks arm64 builds. bionic's signal.h
must be used on those

Change-Id: Id4f07a9b13a32c563fda6e96e4a87b8b97d125fd