config.h now includes the git hash and so, as long as it's included
in solvespace.h, any change of git HEAD will trigger a complete
recompilation, which makes bisecting especially annoying.
While we're at it, remove HAVE_STDINT_H from it, since we require
C++11 and all MSVC versions that include C++11 also include stdint.h.
In principle, GTK3 is the way forward, and GTK2 is officially
deprecated, though still maintained. In practice however, GTK3
is often unbearably buggy; e.g. on my system, combo boxes
don't ever roll up in GTK3 windows. So I have added support
for both.
This required a few minor changes to the core, namely:
* GTK wants to know beforehand whether a menu item is a check
menu item or a regular one.
* GTK doesn't give us an easy way to execute something after
any event is processed, so an explicit idle timer is added.
This is a no-op on Win32.
* A few function signatures were const'ed, since GTK expects
immutable strings when converting to Glib::ustring.
