Modify make_deps to download boost 1.61

This modifies the helper make_deps.sh script to download
Boost 1.6.1, rather than the previous 1.5.1 version.  At
least for now, the URL for the download points to
Sourceforge rather than csubich's public-facing web presence
on belize.math.uwaterloo.ca.

If Sourceforge shuts down, or if Boost moves its historic
releases off the site, then this will need modified.

make_deps.sh

@@ -181,16 +181,17 @@ if [ ! "$BUILD_BOOST" = "yes" ]; then
    echo "NOT building libboost"
 else
    echo "Building libboost"
-   if [ ! -e "boost_1_51_0.tar.gz" ]; then
-      wget http://belize.math.uwaterloo.ca/~csubich/redist/boost_1_51_0.tar.gz
+   if [ ! -e "boost_1_61_0.tar.gz" ]; then
+      #wget http://belize.math.uwaterloo.ca/~csubich/redist/boost_1_51_0.tar.gz
+      wget https://sourceforge.net/projects/boost/files/boost/1.61.0/boost_1_61_0.tar.gz
    fi
    # Untar libbost
-   tar -xzvf boost_1_51_0.tar.gz > /dev/null 
+   tar -xzvf boost_1_61_0.tar.gz > /dev/null 
    if [ 0 -ne $? ]; then
       echo "Could not untar libboost" && exit 1
    fi
 
-   pushd boost_1_51_0
+   pushd boost_1_61_0
 
    # Boost has build-specific toolsets, but it does NOT use the CC/CXX
    # variables to detect the proper toolset.  Instead, it goes by a