Include *.inc.js files in `gopherjs build` mode.
Include *.inc.js files in `gopherjs build` mode.

This simply copies the same functionality from ImportPackage(). Perhaps it
should be factored into a common function.

jargv/gopherjs,bpowers/gopherjs,jargv/gopherjs,gopherjs/gopherjs,albrow/gopherjs,Yanjing123/gopherjs,bpowers/gopherjs,Yanjing123/gopherjs,bpowers/gopherjs,albrow/gopherjs,Archs/gopherjs,gopherjs/gopherjs,Yanjing123/gopherjs,Archs/gopherjs,Archs/gopherjs,gopherjs/gopherjs,govlas/gopherjs,albrow/gopherjs,jargv/gopherjs,gopherjs/gopherjs,gopherjs/gopherjs,govlas/gopherjs,govlas/gopherjs