[decompiler] clean up vector detection and add vector float product detection (#638)

* change

* recognize vector float product and update tests

test/decompiler/reference/engine/ui/credits_REF.gc

@@ -4,8 +4,7 @@
 ;; definition for function set-credits-font-color
 ;; INFO: Return type mismatch int vs none.
 (defun set-credits-font-color ((arg0 float))
-  (let ((f0-0 255.0))
-   )
+  255.0
   (dotimes (v1-0 4)
    (let ((f0-2 (* 64.0 arg0)))
     (if (< 128.0 f0-2)
@@ -26,8 +25,7 @@
     (set! (-> *font-work* color-table 32 color v1-0 b) (the int f0-8))
     )
    )
-  (let ((v0-0 0))
-   )
+  0
   (none)
   )
 
@@ -91,8 +89,7 @@
             )
            )
           )
-    (let ((f0-3 1.0))
-     )
+    1.0
     (let ((v1-3 gp-0))
      (set! (-> v1-3 width) (the float 600))
      )
@@ -158,8 +155,7 @@
      )
     )
    )
-  (let ((v0-6 0))
-   )
+  0
   (none)
   )
 

test/decompiler/reference/engine/ui/hud-h_REF.gc

@@ -183,5 +183,4 @@
   )
 
 ;; failed to figure out what this is:
-(let ((v0-8 0))
-  )
+0

test/decompiler/reference/engine/ui/progress-h_REF.gc

@@ -308,5 +308,4 @@
 (define *progress-last-task-index* 0)
 
 ;; failed to figure out what this is:
-(let ((v0-12 0))
-  )
+0

test/decompiler/reference/engine/ui/text-h_REF.gc

@@ -65,5 +65,4 @@
 (define *common-text* (the-as game-text-info #f))
 
 ;; failed to figure out what this is:
-(let ((v0-5 0))
-  )
+0