Add netmask helper functions
Add netmask helper functions

netmask_prefix(): Converts a "A.B.C.D" string into binary, and returns the
number of set bits.

cidr_to_mask(): Converts an integer into a binary mask

srijanmishra/RouteFlow,CPqD/RouteFlow,raphaelvrosa/RouteFlow,raphaelvrosa/RouteFlow,CPqD/RouteFlow,ralph-mikera/RouteFlow-1,c3m3gyanesh/RouteFlow-OpenConfig,arazmj/RouteFlow,rsanger/RouteFlow,raphaelvrosa/RouteFlow,ralph-mikera/RouteFlow-1,ralph-mikera/RouteFlow-1,ralph-mikera/RouteFlow-1,c3m3gyanesh/RouteFlow-OpenConfig,raphaelvrosa/RouteFlow,c3m3gyanesh/RouteFlow-OpenConfig,routeflow/RouteFlow,arazmj/RouteFlow,srijanmishra/RouteFlow,CPqD/RouteFlow,rsanger/RouteFlow,rsanger/RouteFlow,c3m3gyanesh/RouteFlow-OpenConfig,srijanmishra/RouteFlow,ralph-mikera/RouteFlow-1,arazmj/RouteFlow,routeflow/RouteFlow,srijanmishra/RouteFlow,CPqD/RouteFlow,CPqD/RouteFlow,srijanmishra/RouteFlow,rsanger/RouteFlow,c3m3gyanesh/RouteFlow-OpenConfig,c3m3gyanesh/RouteFlow-OpenConfig,rsanger/RouteFlow,arazmj/RouteFlow,arazmj/RouteFlow,ralph-mikera/RouteFlow-1,routeflow/RouteFlow,routeflow/RouteFlow,arazmj/RouteFlow,raphaelvrosa/RouteFlow,routeflow/RouteFlow,raphaelvrosa/RouteFlow,rsanger/RouteFlow