(Doc, Fix) Updated unix library list (PR RavenProject#886)

Added library to build script
Edited libdb++ library -dev

Author: ForTimeBeing

doc/build-unix.md

@@ -48,6 +48,7 @@ These dependencies are required:
  libssl      | Crypto           | Random Number Generation, Elliptic Curve Cryptography
  libboost    | Utility          | Library for threading, data structures, etc
  libevent    | Networking       | OS independent asynchronous networking
+ libdb++     | Utility          | Contains headers and static libraries for the Berkeley DB library
 
 Optional dependencies:
 
@@ -90,7 +91,7 @@ Finally, clang (often less resource hungry) can be used instead of gcc, which is
 
 Build requirements:
 
-    sudo apt-get install build-essential libtool autotools-dev automake pkg-config libssl-dev libevent-dev bsdmainutils python3
+    sudo apt-get install build-essential libtool autotools-dev automake pkg-config libssl-dev libevent-dev bsdmainutils python3 libdb++-dev
 
 Options when installing required Boost library files: