[PATCH 0 of 4 v3 RESEND] xl: add support for vif rate limiting

["Mathieu Gagné" <mgagne@iweb.com>]

Hi,

This patch series implements the required plumbering for vif rate limiting in libxl/xl.

The first patch (already applied) fixes trivial indentation issues and introduces no functional changes.

The second patch (already applied) implements dry-run for `xl network-attach` for debugging and testing purposes.

The third patch adds the required plumbering in libxl/xl to add vif rate limiting support. It uses the `rate` option syntax from xm/xend, ensuring full backward compatiblity.

The final patch adds the "check-xl-vif-parse" test script which tests various `rate` syntax.

Changes in v3:
- Move xlu_cfg_init from parse_vif_rate to main_networkattach
- Add xlu_cfg_destroy to main_networkattach
- Use %"PRIuXX" instead of %llu and %lu

Changes in v2:
- Don't default to unlimited in case of overflow/underflow or invalid syntax in rate
- Add error handling
- Remove use of matches in regex which weren't used anyway
- Add docs about the syntax
- Add note in docs explaining that limitations are netback implementation specific
- Modify test cases according to new behavior

--
Mathieu