core: Make the gpgconf option parsing of string types more robust

* src/engine-gpgconf.c (gpgconf_parse_option): Skip the string
indicator if it is not the empty string.
--

Some versions of GnuPG (~2.2.28 to 2.2.33) returned a compliance
indicator which should be an int but actually used string as type.
Simply skipping the indicator without checking that this is the
indicator does not allow to work around this type mismatch by the
gpgme users.

src/engine-gpgconf.c

@@ -445,7 +445,9 @@ gpgconf_parse_option (gpgme_conf_opt_t opt,
             case GPGME_CONF_PUB_KEY:
             case GPGME_CONF_SEC_KEY:
             case GPGME_CONF_ALIAS_LIST:
-	      /* Skip quote character.  */
+	      /* Skip quote character.  It is required by specs but
+               * technically not always needed.  */
+              if (*line == '\"' && line[1])
                 line++;
 
 	      err = _gpgme_decode_percent_string (line, &arg->value.string,