correct version on boost.mk (#91)

* Update configure.ac

Move BOOST_SYSTEM line to be last to work around weird compile bug

* Also change version to 69

Person who modified this file to change to rev 69 missed changing the version line as well. This caused compiles to fail.

depends/packages/boost.mk

@@ -1,5 +1,5 @@
 package=boost
-$(package)_version=1_64_0
+$(package)_version=1_69_0
 $(package)_download_path=https://dl.bintray.com/boostorg/release/1.69.0/source/
 $(package)_file_name=$(package)_$($(package)_version).tar.bz2
 $(package)_sha256_hash=8f32d4617390d1c2d16f26a27ab60d97807b35440d45891fa340fc2648b04406