contrib: import GtkBitset as EggBitset

This imports GTK's GtkBitset and the underlying roaring bitmaps so that
we will have it without having to use GTK from libsysprof-analyze.

contrib/eggbitset/meson.build

@@ -0,0 +1,17 @@
+libeggbitset_sources = [
+  'eggbitset.c',
+]
+
+libeggbitset_deps = [
+  dependency('gio-2.0', version: glib_req_version),
+]
+
+libeggbitset_static = static_library('eggbitset', libeggbitset_sources,
+  gnu_symbol_visibility: 'hidden',
+           dependencies: libeggbitset_deps,
+)
+
+libeggbitset_static_dep = declare_dependency(
+  include_directories: include_directories('.'),
+            link_with: libeggbitset_static,
+)