Add a compat option to use Unknown's accurate dotprod for VMMUL.

[hrydgard]

And use it to eliminate the long standing problem of Tekken 6 leg shaking. Fixes #5399.

This is kind of hacky, but it's the first use of our (part mine but mostly @unknownbrackets) recent findings about the accuracy of the VFPU dot product, see #2990.

This simply takes the latest version of vfpu_dot from https://github.com/hrydgard/ppsspp/compare/master...unknownbrackets:vfpu-dot?expand=1 (which will need rebasing) and applies it only to vmmul for now, which is enough to eliminate the leg shaking problem in Tekken 6.

It's really just the start, later we will expand the use of these findings, and if performance can be made good enough we'll enable it for all games (with maybe an opt-out for any game that gets hit unusually hard).

[unknownbrackets]

I think there's value to the commits that chaneg the implementation, implement INF * 0 properly, etc.

-[Unknown]

[hrydgard]

Yeah true, I agree - I'll split the commit up and include the various versions.

[LunaMoo]

Here's a more complete compat list of id's:

# Tekken 5 DR
ULJS00048 = true
ULUS10139 = true
UCES00356 = true
ULJS19013 = true
NPJH50137 = true

# Tekken 6
ULUS10466 = true
ULES01376 = true
ULJS00224 = true
NPUH10047 = true
ULAS42214 = true
ULJS19054 = true
NPJH50184 = true

[unknownbrackets]

Created #12217 with the full history (adding on this commit, essentially, although I missed the gitignore change.)

-[Unknown]

[hrydgard]

Closing in favor of #12217.