Colubris Networks Inc., a Waltham start-up that makes wireless networking gear, has closed a $15 million round of venture capital funding that brings its total raised to $36 million. Doll Capital Management led the round. Other firms investing include Prism Venture Partners, Mid-Atlantic Venture Funds, GrandBanks Capital, and the Business Development Bank of Canada. Colubris has amassed more than 1,000 customers deploying ”WiFi” and other wireless network services.