graphics/mesa: Update to 19.0.8

Update mesa and related ports to 19.0.8.
This is the last version where the autotools build system is being used.
This serves as a stepping stone for reworking the ports to use the meson
build system and to enable further updates.

PR: 235570
Submitted by: jbeich (with minor changes)
Differential Revision: https://reviews.freebsd.org/D19099

			https://reviews.freebsd.org/D19100