Fix out of bounds array access in lexer

If the type char is signed, then in the function
yylex_GetFloatMaskAndFloatLen(), *s can have a negative value and be converted
to a negative int32_t which is then used as an array index. It should be
converted to uint8_t instead to ensure that the value is in the bounds of the
tFloatingFirstChar, tFloatingSecondChar, and tFloatingChars arrays.

src/asm/lexer.c

@@ -471,17 +471,17 @@ void yylex_GetFloatMaskAndFloatLen(uint32_t *pnFloatMask, uint32_t *pnFloatLen)
 
 	char *s = pLexBuffer;
 	uint32_t nOldFloatMask = 0;
-	uint32_t nFloatMask = tFloatingFirstChar[(int32_t)*s];
+	uint32_t nFloatMask = tFloatingFirstChar[(uint8_t)*s];
 
 	if (nFloatMask != 0) {
 		s++;
 		nOldFloatMask = nFloatMask;
-		nFloatMask &= tFloatingSecondChar[(int32_t)*s];
+		nFloatMask &= tFloatingSecondChar[(uint8_t)*s];
 
 		while (nFloatMask != 0) {
 			s++;
 			nOldFloatMask = nFloatMask;
-			nFloatMask &= tFloatingChars[(int32_t)*s];
+			nFloatMask &= tFloatingChars[(uint8_t)*s];
 		}
 	}
 

test/asm/garbage_char.asm

@@ -0,0 +1 @@
+x<EFBFBD>

test/asm/garbage_char.out

@@ -0,0 +1,3 @@
+ERROR: garbage_char.asm(1):
+    syntax error
+error: Assembly aborted (1 errors)!

test/asm/garbage_char.out.pipe

@@ -0,0 +1,3 @@
+ERROR: -(1):
+    syntax error
+error: Assembly aborted (1 errors)!