Update changelog for 2.10.0rc2

Signed-off-by: Olivier Mehani <olivier.mehani@nicta.com.au>
Use INT64_MAX and multiplications rather than bitshifts for log rate limitation

fixes: #1130

Signed-off-by: Olivier Mehani <olivier.mehani@nicta.com.au>
[scaffold] Fix handling of POPT default values

The val element of the poptOption struct is not meant to hold a default
value, but a *return* value for poptGetNextOpt upon encountering the
option; 0 indicate not to return.

oml2-scaffold sets this value to the short-hand character for the
option, or 0 if not specified.

Signed-off-by: Olivier Mehani <olivier.mehani@nicta.com.au>
Handle --oml-noop better, and document

Signed-off-by: Olivier Mehani <olivier.mehani@nicta.com.au>