[PATCH 0 of 4 v2] 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 fixes trivial indentation issues and introduces no functional changes.

The second patch 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 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

Please comment on the overflow and error handling.

Sorry for the delay.

--
Mathieu