docs: Update OpenBSD build instructions for OpenBSD 6.3

doc/build-openbsd.md

@@ -1,6 +1,6 @@
 OpenBSD build guide
 ======================
-(updated for OpenBSD 6.2)
+(updated for OpenBSD 6.3)
 
 This guide describes how to build bitcoind and command-line utilities on OpenBSD.
 
@@ -12,11 +12,10 @@ Preparation
 Run the following as root to install the base dependencies for building:
 
 ```bash
-pkg_add git gmake libevent libtool
+pkg_add git gmake libevent libtool boost
 pkg_add autoconf # (select highest version, e.g. 2.69)
 pkg_add automake # (select highest version, e.g. 1.15)
 pkg_add python # (select highest version, e.g. 3.6)
-pkg_add boost
 
 git clone https://github.com/bitcoin/bitcoin.git
 ```
@@ -55,8 +54,15 @@ export BDB_PREFIX="$PWD/db4"
 
 Preparation:
 ```bash
-export AUTOCONF_VERSION=2.69 # replace this with the autoconf version that you installed
-export AUTOMAKE_VERSION=1.15 # replace this with the automake version that you installed
+
+# Replace this with the autoconf version that you installed. Include only
+# the major and minor parts of the version: use "2.69" for "autoconf-2.69p2".
+export AUTOCONF_VERSION=2.69
+
+# Replace this with the automake version that you installed. Include only
+# the major and minor parts of the version: use "1.15" for "automake-1.15.1".
+export AUTOMAKE_VERSION=1.15
+
 ./autogen.sh
 ```
 Make sure `BDB_PREFIX` is set to the appropriate path from the above steps.