gobject properties and file entries

[Kai Willadsen <kai willadsen gmail com>]

Hi,

It turns out that the gobject property API used in History*Entry was
added in 2.13.2 (July 2007). This breaks file selection and other
parts of Meld on older distributions (see bug 575855). As a result of
this bug, and inspired by Vincent's recent patches, I've just
committed a significant rework of HistoryEntry and HistoryFileEntry.
I've tested the reworked widgets as best I can, but it needs wider
testing.

So, this is a call for testing for meld svn. Specifically, please test
the behaviour of the history-saving widgets (mainly the file entries)
and file bugs.

Kai