Add equality operator between string_view and char*

Hi,
boost::string_ref don't have an equality operator between string_view and char*, so I added one

It first compare using std::equal and if it return true then search if we are at the end of the char*

I didn't search first for the possible \0 charter at size() + 1 because possible memory check made by OS/C++ runtime (or it's safe?)

I'm just started learning C++, so I don't know if this commit it's ok

The test suite for uri it's all green