libparted: sync partitions > 16

The linux partition sync code was hard coded to only flush
the first 16 partitions.
ui: switch to new-style readline typedef

The CPPFunction typedef (among others) have been deprecated in favour of
specific prototyped typedefs since readline 4.2 (circa 2001).
It's been working since because compatibility typedefs have been in
place until they where removed in the recent readline 6.3 release.
Switch to the new style to avoid build breakage.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>