[OpenGL] Golden Sun: Some NPCs' position gets slightly displaced compared to Software mode

[RafaelTrepaUnCarballo]

Some NPCs and sometimes even the main character are moved a bit to the left in OpenGL mode (in any resolution, even x1)

Software: OpenGL:

Animated comparison:

Present in the last build 0.10-7565-0dce8b392 , both for Windows x86_64 and Switch European Spanish Rom c63008d6

[endrift]

This appears to be related to transformation rounding, especially when the 0,0 component of the transformation matrix is negative. I managed to redo the origin so it matches the software renderer when it's set to 1× scaling, but at anything else it introduces pixel gaps due to the origins of sprites no longer being the top left. It's gonna take some experimentation to fix.