Add MS BASIC equality test in similarity.c

Plus fixing mistakes

src/basic/math/b947.inv_FAC1.s

@@ -39,6 +39,7 @@ inv_FAC1_mantissa:
     lda FACOV
     eor #$FF
     sta FACOV
+    inc FACOV
     bne inc_FAC1_ret
     
     ; Fallthrough to inc_FAC1

src/basic/math/b983.shiftr_FAC.s

@@ -45,7 +45,7 @@ shiftr_FAC:
     sbc #8              ; Go back to previous value
     tay
     lda FACOV
-    bcs shiftr_FAC
+    bcs shftrt
 .sext:
     asl 1,X
     bcc @2

src/basic/math/bc1b.round_FAC1.jmp.s

@@ -5,5 +5,6 @@
 
 ; Just a compatibility jump - our routine is longer than original one
 
-	jmp round_FAC1
+round_FAC1:
+	jmp round_FAC1_impl
 	

src/basic/math/round_FAC1.s

@@ -12,7 +12,7 @@
 
 ; XXX test this
 
-round_FAC1:
+round_FAC1_impl:
 
 	; If number is 0, do not do anything