Pull via http to avoid certificate errors with https on certain platforms

(Illumos, SmartOS, Solaris... I'm looking at you.) Speed up builds by
running make in parallel (use all the cores!).

c_src/build_deps.sh

@@ -21,13 +21,12 @@ case "$1" in
                 git fetch && \
                 git merge origin/$WT_BRANCH)
         else
-	    git clone https://github.com/wiredtiger/wiredtiger.git -b $WT_BRANCH && \
+            git clone http://github.com/wiredtiger/wiredtiger.git -b $WT_BRANCH && \
                 (cd wiredtiger && ./autogen.sh)
         fi
         (cd wiredtiger/build_posix && \
             ../configure --with-pic \
                          --prefix=$BASEDIR/system && \
-            make && make install)
+            make -j 8 && make install)
         ;;
 esac
-