build: require Boost >= 1.74.0

Change-Id: I654040f2069f58d53804b73780e54e31dccfdb48

Author: Pesa

docs/beginners-guide.rst

@@ -118,7 +118,7 @@ should be run as root:
 
        $ dnf list --installed openssl-devel
 
-#. Boost libraries version 1.71.0 or later
+#. Boost libraries version 1.74.0 or later
 
    ::
 

wscript

@@ -73,8 +73,8 @@ def configure(conf):
                    uselib_store='NDN_CXX', pkg_config_path=pkg_config_path)
 
     conf.check_boost()
-    if conf.env.BOOST_VERSION_NUMBER < 107100:
-        conf.fatal('The minimum supported version of Boost is 1.71.0.\n'
+    if conf.env.BOOST_VERSION_NUMBER < 107400:
+        conf.fatal('The minimum supported version of Boost is 1.74.0.\n'
                    'Please upgrade your distribution or manually install a newer version of Boost.\n'
                    'For more information, see https://redmine.named-data.net/projects/nfd/wiki/Boost')