Allow using multiple ttf files with separate styles of same family

[pulsejet]

This is done by keeping a BoostHash of all the styles we have and their corresponding paths, and passing the style when we want to get the font.

[carstene1ns]

I really hoped we could be boost-free nowadays... 😞

[pulsejet]

@carstene1ns BoostHash is not boost xD. I'm using it just for consistency. This actually would make it easier if we wanted to transition that class to C++11 (you can literally replace all instances of boost::unordered_map in boost-hash.h with std::map and it just works; do the same thing for unordered_set and you no longer need to compile boost).

[Ancurio]

Yeah, I wrote BoostHash just to mimic the API of QHash, its predecessor.

[Ghabry]

@pulsejet well there is still boost::program_options which is not trivial to replace or do you have an alternative for this? :o