[decompiler] recognize vector-dot

[water111]

it shows up a lot.

It would be cool to do this in a general way, in case there are other commonly inlined asm functions that could be recognized.
Luckily the registers always end up the same, this was an asm function with manually specified registers and the allocator didn't run on these

    lwc1 f0, 0(a0)
    lwc1 f1, 4(a0)
    lwc1 f2, 8(a0)
    lwc1 f3, 12(a0)
    lwc1 f4, 0(a1)
    lwc1 f5, 4(a1)
    lwc1 f6, 8(a1)
    lwc1 f7, 12(a1)
    mula.s f0, f4
    madda.s f1, f5
    madda.s f2, f6
    madd.s f0, f3, f7
    mfc1 v0, f0
    jr ra
    daddu sp, sp, r0

[water111]

This was implemented for the 3 dimensional case vector-dot in #560 but not 4 vector4-dot. An example of 4 is ray-arbitrary-circle-intersect.

In general, this type of detection works, but fails to build it into expressions in a nice way automatically. It is an unfortunate limitation of the decompiler framework but I don't really know how to fix it.

[water111]

now tracked in #636