Rename EXTRACT_QUOTES to EXTRACT_UNQUOTE

Whenever I see EXTRACT_QUOTES, I'm always confused whether it means to
leave the quotes in or to take them out. Let's say "unquote", like we
say "cunescape".

src/basic/extract-word.c

@@ -135,7 +135,7 @@ int extract_first_word(const char **p, char **ret, const char *separators, Extra
                         for (;; (*p)++, c = **p) {
                                 if (c == 0)
                                         goto finish_force_terminate;
-                                else if (IN_SET(c, '\'', '"') && (flags & EXTRACT_QUOTES)) {
+                                else if (IN_SET(c, '\'', '"') && (flags & EXTRACT_UNQUOTE)) {
                                         quote = c;
                                         break;
                                 } else if (c == '\\' && !(flags & EXTRACT_RETAIN_ESCAPE)) {