feat(asm&go4k): Preprocess asm code using go text/template

The preprocessing is done sointu-cli and (almost) nothing is done by the NASM preprocessor anymore (some .strucs are still there.
Now, sointu-cli loads the .yml song, defines bunch of macros (go functions / variables) and passes the struct to text/template parses.
This a lot more powerful way to generate .asm code than trying to fight with the nasm preprocessor.

At the moment, tests pass but the repository is a bit of monster, as the library is still compiled using the old approach. Go should
generate the library also from the templates.

templates/flowcontrol.asm

@@ -0,0 +1,23 @@
+{{- if .Opcode "speed" -}}
+;-------------------------------------------------------------------------------
+;   SPEED opcode: modulate the speed (bpm) of the song based on ST0
+;-------------------------------------------------------------------------------
+;   Mono: adds or subtracts the ticks, a value of 0.5 is neutral & will7
+;   result in no speed change.
+;   There is no STEREO version.
+;-------------------------------------------------------------------------------
+{{.Func "su_op_speed" "Opcode"}}
+{{- .Float 2.206896551724138 | .Prepare | indent 4}}
+    fmul    dword [{{.Float 2.206896551724138 | .Use}}]         ; (2*s-1)*64/24, let's call this p from now on
+    {{.Call "su_power"}}
+    fld1                                 ; 1 2^p
+    fsubp   st1, st0                     ; 2^p-1, the player is advancing 1 tick by its own
+    fadd    dword [{{.WRK}}] ; t+2^p-1, t is the remainder from previous rounds as ticks have to be rounded to 1
+    push    {{.AX}}
+    fist    dword [{{.SP}}]                  ; Main stack: k=int(t+2^p-1)
+    fisub   dword [{{.SP}}]                  ; t+2^p-1-k, the remainder
+    pop     {{.AX}}
+    add     dword [{{.Stack "Sample"}}], eax          ; add the whole ticks to row tick count
+    fstp    dword [{{.WRK}}] ; save the remainder for future
+    ret
+{{end}}