Bridge: vlan_add and vlan_del

* new macros in switch/linux/linux.h to open and close
sockets to control 8021q and bridge modules
* vlan_add an vlan_del Switch API functions implemented
with "bridge" module
* definition of vif_add and vif_del
* use IMPL Linux in switch/Makefile to compile with "bridge"
and "8021q" implementation; same thing for "tools" applications

Signed-off-by: Claudiu Ghioc <claudiu.ghioc@gmail.com>