Fix references to unknown 'external' directory; make this project self-contained
Missing files from Bionic: NDK copy of <sched.h> no longer defines cpu_set_t
Cannot have two modules both named libudev, so renaming the static one to libudev_static
Use awk (comes with NDK) instead of head (requires Unix or cygwin)
Avoid warnings on endianess defines
These syscalls are already defined in modern NDKs (r9d)
__USE_GNU is needed for <sched.h> to define cpu_set_t.
Meanwhile, _GNU_SOURCE is defined in NDK <features.h>.
Export libudev includes to modules that depend on it.