libsigc++: bump to 2.3.2

Signed-off-by: Marc-Antoine Perennou <keruspe@exherbo.org>
vala: add 0.25.1

Signed-off-by: Marc-Antoine Perennou <keruspe@exherbo.org>
app-editors/vim-runmtime: enable syntax highlighting as default

Change-Id: I3aefbdd8c9c16665b34556457d286cfe62fe383d