util: Don't interpret quotes by default in extract_first_word

This adds an EXTRACT_QUOTES option to allow the previous behaviour, of
not interpreting any character inside ' or " quotes as separators.

src/basic/util.h

@@ -858,6 +858,7 @@ typedef enum ExtractFlags {
         EXTRACT_RELAX           = 1,
         EXTRACT_CUNESCAPE       = 2,
         EXTRACT_CUNESCAPE_RELAX = 4,
+        EXTRACT_QUOTES          = 8,
 } ExtractFlags;
 
 int extract_first_word(const char **p, char **ret, const char *separators, ExtractFlags flags);