Tools: Use GCC 4.9 as an Ubuntu prereq

This should actually use the install-prereq script so we don't duplicate
effort on the maintenance of these scripts. But let's at least install
the correct version for now.

Tools/vagrant/initvagrant.sh

@@ -10,7 +10,7 @@ PYTHON_PKGS="pymavlink MAVProxy droneapi"
 PX4_PKGS="python-serial python-argparse openocd flex bison libncurses5-dev \
           autoconf texinfo build-essential libftdi-dev libtool zlib1g-dev \
           zip genromfs"
-UBUNTU64_PKGS="libc6:i386 libgcc1:i386 gcc-4.6-base:i386 libstdc++5:i386 libstdc++6:i386"
+UBUNTU64_PKGS="libc6:i386 libgcc1:i386 gcc-4.9-base:i386 libstdc++5:i386 libstdc++6:i386"
 
 # GNU Tools for ARM Embedded Processors
 # (see https://launchpad.net/gcc-arm-embedded/)