Update meson to 0.48.0.

This version brings python 3.7 support. For detailed changelog see:
http://mesonbuild.com/Release-notes-for-0-47-0.html
http://mesonbuild.com/Release-notes-for-0-48-0.html

Exp-run by: antoine@

PR: 231219
Submitted by: Tamas Szakaly <sghctoma@gmail.com> (update to 0.47.2),

		Ting-Wei Lan <lantw44@gmail.com> (update to 0.48.0)