Removing "using namespace std" everywhere.

src/compiler/cpp_generator.cc

src/compiler/cpp_generator.h

src/compiler/cpp_generator_helpers.h

src/compiler/cpp_plugin.cc

src/compiler/ruby_generator.cc

src/compiler/ruby_generator.h

src/compiler/ruby_generator_helpers-inl.h

src/compiler/ruby_generator_map-inl.h

src/compiler/ruby_generator_string-inl.h

src/compiler/ruby_plugin.cc