Holding left and right at the same time while L+R is disabled causes left to take priority.

What steps will reproduce the problem?
1. Open any SNES game where you control a character using left and right
2. Make sure "Allow U+D/L+R" is not checked
3. Hold left and right at the same time

What is the expected output? What do you see instead?
The expected output is that the left and right cancel eachother out and neither 
registers as being pressed. Instead, the left will take priority.

What version of the product are you using? On what operating system?
Using version 1.8.1 on Windows 7 professional.

Please provide any additional information below.
This is a problem because when switching from left to right with a keyboard 
there is often a brief period where you are holding left and right at the same 
time. The current asymmetrical behavior of having left take priority means that 
certain character maneuvers will have to be done differently in the right 
direction vs the left direction to take into account the bias towards the left.

The same thing happens with holding up and down at the same time: the up takes 
priority.

Original issue reported on code.google.com by jeff.wil...@gmail.com on 13 Sep 2014 at 6:51

a65090482 / bizhawk

Holding left and right at the same time while L+R is disabled causes left to take priority. #264