Files are installed into the root directory

[yurivict]

@lvandeve

This commit on Sep 12, 2017 broke Makefile:
be5491d

Now it doesn't install libraries into $(PREFIX). It installs them into root.

Now installed files look like this:

/highwayhash/arch_specific.h
/highwayhash/c_bindings.h
/highwayhash/compiler_specific.h
/highwayhash/data_parallel.h
/highwayhash/endianess.h
/highwayhash/hh_avx2.h
/highwayhash/hh_buffer.h
/highwayhash/hh_portable.h
/highwayhash/hh_sse41.h
/highwayhash/hh_types.h
/highwayhash/hh_vsx.h
/highwayhash/highwayhash.h
/highwayhash/highwayhash_target.h
/highwayhash/highwayhash_test_target.h
/highwayhash/iaca.h
/highwayhash/instruction_sets.h
/highwayhash/load3.h
/highwayhash/nanobenchmark.h
/highwayhash/os_specific.h
/highwayhash/profiler.h
/highwayhash/robust_statistics.h
/highwayhash/scalar.h
/highwayhash/scalar_sip_tree_hash.h
/highwayhash/sip_hash.h
/highwayhash/sip_tree_hash.h
/highwayhash/state_helpers.h
/highwayhash/tsc_timer.h
/highwayhash/vector128.h
/highwayhash/vector256.h
/highwayhash/vector_test_target.h
/libhighwayhash.a
/libhighwayhash.so
/libhighwayhash.so.0

[jan-wassenberg]

Oops, looks like we somehow removed the following from Makefile:

PREFIX ?= /usr/local	
INCDIR ?= $(PREFIX)/include	
LIBDIR ?= $(PREFIX)/lib

I've added this to TODO - thanks for reporting!

[yurivict]

This is still broken.

[jan-wassenberg]

At long last :) Sorry about the delay, we have been very busy.