Add meson build
Note: there's still a warning that I wasn't able to fix, during gi-scan, and which doesn't appear in the autotools build:
<unknown>:: Warning: Xfconf: (ErrorQuarkFunction)get_error_quark: xfconf_get_error_quark: Couldn't find corresponding enumeration
It shouldn't be too serious, it doesn't affect the doc, but maybe the vala binding.
EDIT: fixed in 430d3c8a
Edited by Gaël Bonithon