Redefine the trig functions to divide circles into 1.0 turns (#1060)

This makes their behavior consistent across Q settings

Fixes #1059

test/asm/trigonometry.asm

@@ -0,0 +1,38 @@
+for Q, 2, 31
+	OPT Q.{d:Q}
+
+	assert sin(0.25) == 1.0
+	assert asin(1.0) == 0.25
+
+	assert sin(0.0) == 0.0
+	assert asin(0.0) == 0.0
+
+	assert cos(0.0) == 1.0
+	assert acos(1.0) == 0.0
+
+	if Q > 2 ; can't represent 0.125 in Q.2
+		assert tan(0.125) == 1.0
+		assert atan(1.0) == 0.125
+	else
+		assert tan(0.0) == 0.0
+		assert atan(0.0) == 0.0
+	endc
+endr
+
+SECTION "sine", ROM0[0]
+OPT Q.16
+; Generate a table of sine values from sin(0.0) to sin(1.0), with
+; amplitude scaled from [-1.0, 1.0] to [0.0, 128.0]
+DEF turns = 0.0
+REPT 256
+    db MUL(64.0, SIN(turns) + 1.0) >> 16
+    DEF turns += 1.0 / 256
+ENDR
+
+
+SECTION "cosine", ROM0[256]
+OPT Q.8
+; 32 samples of cos(x) from x=0 to x=pi radians=0.5 turns
+for x, 0.0, 0.5, 0.5 / 32
+    dw cos(x)
+endr