Add noError option for OpenGL and misc. fixes

It makes OpenGL use CONTEXT_FLAG_NO_ERROR_BIT_KHR flag. Currently GLX-only.

• Fix -t/--trillinear option having no effect. Already fixed in master. Whoops.
• Don't modify constant memory in Vulkan. Fixes yuzu crashes with certain flags.
• Use correct variable, fixes VSync setting on vulkan.

P.S.: waiting for updated dlsym to get merged into master.