- Fixed all warnings, for renderer_opengl items, which were indicating a
possible incorrect behavior from integral promotion rules and types
larger than those in which arithmetic is typically performed.
- Added const for variables where possible and meaningful.
- Added constexpr where possible.
The std::string generation with its malloc and free requirement
was a noticeable overhead. Also switch to an ordered_map to
avoid the std::hash call. As those maps usually have a size of
two elements, the lookup time shall not matter.
Given std::vector is a type with a non-trivial destructor, this
variable cannot be optimized away by the compiler, even if unused.
Because of that, something that was intended to be fairly lightweight,
was actually allocating 32KB and deallocating it at the end of the
function.