Set minimum required Boost to 1.47.0

fanquake · fanquake · commit 6dd37237222f · 2016-10-17T11:43:59.000+08:00
diff --git a/configure.ac b/configure.ac
@@ -589,8 +589,11 @@ fi
 
 if test x$use_boost = xyes; then
 
+dnl Minimum required Boost version
+define(MINIMUM_REQUIRED_BOOST, 1.47.0)
+
 dnl Check for boost libs
-AX_BOOST_BASE
+AX_BOOST_BASE([MINIMUM_REQUIRED_BOOST])
 AX_BOOST_SYSTEM
 AX_BOOST_FILESYSTEM
 AX_BOOST_PROGRAM_OPTIONS
