Added debian packaging artifacts
Merge pull request #252 from larsbutler/deb-pkg

Add debian packaging artifacts
Makefile: remove unnecessary setting of DESTDIR

Using an undefined variable is not an error -- the variable is simply
replaced by the empty string. The GNU Coding Standards concurs:

  You should not set the value of DESTDIR in your Makefile at all;
  then the files are installed into their expected locations by
  default. Also, specifying DESTDIR should not change the operation of
  the software in any way, so its value should not be included in any
  file contents.

  http://www.gnu.org/prep/standards/html_node/DESTDIR.html
Use LDFLAGS when compiling zerovm

This lets the compiler find libvalidator correctly when it is
installed under PREFIX/lib and zerovm is compilsed using the same
PREFIX setting.

This removes the "need" to run 'sudo make install' when installing the
validator, e.g., the library can be installed in a custom location be
found without further hacking of the zerovm Makefile.
Makefile: use bindir and nacl_includedir variables
Merge pull request #253 from mgeisler/use-ldflags

Use LDFLAGS
Merge pull request #254