kconfig: rename a variable in the lexer to a clearer name

In Kconfig, like Python, you can enclose a string by double-quotes or
single-quotes. So, both "foo" and 'foo' are allowed.

The variable, "str", is used to remember whether the string started with
a double-quote or a single-quote because open/closing quotation marks
must match.

The name "str" is too generic to understand the intent. Rename it to
"open_quote", which is easier to understand. The type should be 'char'.

Signed-off-by: Masahiro Yamada <[e-mail]>
Reviewed-by: Boris Kolpackov <[e-mail]>

scripts/kconfig/lexer.l

···
 n	[A-Za-z0-9_-]
 
 %%
-	int str = 0;
+	char open_quote = 0;
 
 #.*			/* ignore comment */
 [ \t]*			/* whitespaces */
···
 ":="			return T_COLON_EQUAL;
 "+="			return T_PLUS_EQUAL;
 \"|\'			{
-				str = yytext[0];
+				open_quote = yytext[0];
 				new_string();
 				BEGIN(STRING);
 			}
···
 		append_string(yytext + 1, yyleng - 1);
 	}
 	\'|\"	{
-		if (str == yytext[0]) {
+		if (open_quote == yytext[0]) {
 			BEGIN(INITIAL);
 			yylval.string = text;
 			return T_WORD_QUOTE;