Implement . string constant for the current label scope (#1499)

src/asm/lexer.cpp

@@ -327,8 +327,6 @@ static std::unordered_map<std::string, int, CaseInsensitive, CaseInsensitive> ke
     {"POPO",          T_(POP_POPO)         },
 
     {"OPT",           T_(POP_OPT)          },
-
-    {".",             T_(PERIOD)           },
 };
 
 static bool isWhitespace(int c) {
@@ -1173,6 +1171,10 @@ static Token readIdentifier(char firstChar, bool raw) {
 			return Token(search->second);
 	}
 
+	// Label scope `.` is the only nonlocal identifier that starts with a dot
+	if (identifier.find_first_not_of('.') == identifier.npos)
+		tokenType = T_(ID);
+
 	return Token(tokenType, identifier);
 }