required g++ version number

Author: Daniel Kroening

COMPILING

@@ -38,6 +38,8 @@ We assume that you have a Debian/Ubuntu or Red Hat-like distribution.
 
    yum install gcc gcc-c++ flex bison perl-libwww-perl patch
 
+   Note that you need g++ version 4.9 or newer.
+
 1) As a user, get the CBMC source via
 
    git clone https://github.com/diffblue/cbmc cbmc-git