Please add missing lib for Ubuntu 18.04

[skironDotNet]

When trying to build navcoin-core ./configure (to be exact) I was getting this error:

checking for Berkeley DB C++ headers... no
configure: error: libdb_cxx headers missing, Navcoin Core requires this library for wallet functionality (--disable-wallet to disable wallet functionality)

needed this lib to make it work
sudo apt-get install -y libdb5.3++-dev

So basically on Ubuntu 18.04 this lib was present after running your script libdb5.3++ but also need libdb5.3++-dev

[mxaddict]

@skironDotNet libdb is usually build from the depends dir, if you install libdb from ubuntu, you would be using system version, but should still work.