wireframe: optimize away unncessary getter calls

We've got lots of getter function calls, just to retrieve some pointers
that are used many times in the same function - which is unncessary
boilerplate and consumes extra cycles. It's enough to fetch them once
and keep them on stack/register.

Since wireframeDraw*() are static and have exactly one caller, the
compiler can rewrite them to use the parameters from caller's stack,
effectively inline these functions.

X-Feature-Add: wireframe-optimize-vars
x-Base: master
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>