Import Upstream version 2.72.4

HACKING

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+If you want to hack on the GLib project, you'll need to have the
+following packages installed:
+
+        - Meson 0.48.0
+        - GNU gettext 0.10.40
+        - pkg-config 0.16
+        - gtk-doc
+        - libffi 3.0.0
+
+To compile a Git version of glib on your system, you will need to take
+several steps to setup the tree for compilation.  You can do all these
+steps at once by running:
+
+        checkout/glib# meson _build
+
+For information about submitting patches see the CONTRIBUTING.md file. For
+information about major design decisions, see the README.rationale file.