Make type specific add functions
Make type specific add functions

Basically, move type specific code into their own functions instead
of making `add` a giant function responsible for everything.

raulgrell/zig,zig-lang/zig,raulgrell/zig,zig-lang/zig,andrewrk/zig,raulgrell/zig,raulgrell/zig,zig-lang/zig,raulgrell/zig,andrewrk/zig