Added other tools required to build protoc 
Added other tools required to build protoc 

I needed to install autoconf and libtool and also added g++. It might not be obvious for some users just wanting to experiment with grpc web and suddenly have to compile a c/c++ program.
grpc/grpc-web,grpc/grpc-web,grpc/grpc-web,grpc/grpc-web,grpc/grpc-web,grpc/grpc-web,grpc/grpc-web