Update OpenBSD and FreeBSD build steps

Re-try with most recent versions, and use BDB_CFLAGS/BDB_LIBS to
directly point at BerkeleyDB instead of CPPFLAGS hacks.

Author: laanwj

doc/build-openbsd.md

@@ -1,6 +1,6 @@
 OpenBSD build guide
 ======================
-(updated for OpenBSD 5.9)
+(updated for OpenBSD 6.0)
 
 This guide describes how to build bitcoind and command-line utilities on OpenBSD.
 
@@ -124,7 +124,7 @@ To configure with wallet:
 ```bash
 ./configure --with-gui=no --with-boost=$BOOST_PREFIX \
     CC=egcc CXX=eg++ CPP=ecpp \
-    LDFLAGS="-L${BDB_PREFIX}/lib/" CPPFLAGS="-I${BDB_PREFIX}/include/"
+    BDB_LIBS="-L${BDB_PREFIX}/lib -ldb_cxx-4.8" BDB_CFLAGS="-I${BDB_PREFIX}/include"
 ```
 
 To configure without wallet:
@@ -142,6 +142,8 @@ gmake check
 Clang (not currently working)
 ------------------------------
 
+WARNING: This is outdated, needs to be updated for OpenBSD 6.0 and re-tried.
+
 Using a newer g++ results in linking the new code to a new libstdc++.
 Libraries built with the old g++, will still import the old library.
 This gives conflicts, necessitating rebuild of all C++ dependencies of the application.

doc/build-unix.md

@@ -315,7 +315,7 @@ For further documentation on the depends system see [README.md](../depends/READM
 Building on FreeBSD
 --------------------
 
-(Updated as of FreeBSD 10.3)
+(Updated as of FreeBSD 11.0)
 
 Clang is installed by default as `cc` compiler, this makes it easier to get
 started than on [OpenBSD](build-openbsd.md). Installing dependencies:
@@ -337,7 +337,7 @@ with 4.8-built Bitcoin Core is needed follow the steps under "Berkeley DB" above
 Then build using:
 
     ./autogen.sh
-    ./configure --with-incompatible-bdb CPPFLAGS=-I/usr/local/include/db5 LDFLAGS=-L/usr/local/lib/db5
+    ./configure --with-incompatible-bdb BDB_CFLAGS="-I/usr/local/include/db5" BDB_LIBS="-L/usr/local/lib -ldb_cxx-5"
     make
 
 *Note on debugging*: The version of `gdb` installed by default is [ancient and considered harmful](https://wiki.freebsd.org/GdbRetirement).