Allow fixed-point constants to have unsigned range (#1084)

For example with Q.4, $F0 is 15.0, which no longer warns

src/asm/lexer.c

@@ -1179,7 +1179,7 @@ static uint32_t readFractionalPart(uint32_t integer)
 		precision = fixPrecision;
 	}
 
-	if (integer >= ((uint32_t)1 << (precision - 1)))
+	if (integer >= ((uint64_t)1 << precision))
 		warning(WARNING_LARGE_CONSTANT, "Magnitude of fixed-point constant is too large\n");
 
 	// Cast to unsigned avoids undefined overflow behavior

test/asm/fixed-point-magnitude.asm

@@ -0,0 +1,13 @@
+OPT Q.4
+println 1.0
+println -1.0
+println 0.0625
+println -0.0625
+println 7.25
+println -7.25
+println 12.25
+println -12.25
+println 15.9375
+println -15.9375
+println 20.0
+println -20.0

test/asm/fixed-point-magnitude.err

@@ -0,0 +1,4 @@
+warning: fixed-point-magnitude.asm(12): [-Wlarge-constant]
+    Magnitude of fixed-point constant is too large
+warning: fixed-point-magnitude.asm(13): [-Wlarge-constant]
+    Magnitude of fixed-point constant is too large

test/asm/fixed-point-magnitude.out

@@ -0,0 +1,12 @@
+$10
+$FFFFFFF0
+$1
+$FFFFFFFF
+$74
+$FFFFFF8C
+$C4
+$FFFFFF3C
+$FF
+$FFFFFF01
+$140
+$FFFFFEC0

test/asm/opt-Q.err

@@ -1,5 +1,3 @@
-warning: opt-Q.asm(10) -> opt-Q.asm::REPT~1(12) -> opt-Q.asm::test(5): [-Wlarge-constant]
-    Magnitude of fixed-point constant is too large
 error: opt-Q.asm(17) -> opt-Q.asm::test(3):
     Argument for option 'Q' must be between 1 and 31
 error: opt-Q.asm(18) -> opt-Q.asm::test(3):