AAA Does not clear upper nibble

[AshTS]

The algorithm performed by the ASCII Adjust After Addition instruction is documented as always clearing the upper nibble of AL. However, the current implementation does not do so.

From https://www.felixcloutier.com/x86/aaa:

IF 64-Bit Mode
    THEN
        #UD;
    ELSE
        IF ((AL AND 0FH) > 9) or (AF = 1)
            THEN
                AX := AX + 106H;
                AF := 1;
                CF := 1;
            ELSE
                AF := 0;
                CF := 0;
        FI;
        AL := AL AND 0FH;
FI;

This can be fixed by adding the bitwise and in the aaa implementation.